diff --git a/src/rpc/channels.ts b/src/rpc/channels.ts
index 4e592985e2..1e3054deb9 100644
--- a/src/rpc/channels.ts
+++ b/src/rpc/channels.ts
@@ -45,16 +45,11 @@ export type SerializedArgument = {
   handles: Channel[],
 };
 
-export type AXNodeValue = string | number;
-
-export type AXNodeChecked = boolean | 'mixed';
-
-export type AXNodePressed = boolean | 'mixed';
-
 export type AXNode = {
   role: string,
   name: string,
-  value?: AXNodeValue,
+  valueString?: string,
+  valueNumber?: number,
   description?: string,
   keyshortcuts?: string,
   roledescription?: string,
@@ -68,8 +63,8 @@ export type AXNode = {
   readonly?: boolean,
   required?: boolean,
   selected?: boolean,
-  checked?: AXNodeChecked,
-  pressed?: AXNodePressed,
+  checked?: 'checked' | 'unchecked' | 'mixed',
+  pressed?: 'pressed' | 'released' | 'mixed',
   level?: number,
   valuemin?: number,
   valuemax?: number,
@@ -80,15 +75,6 @@ export type AXNode = {
   children?: AXNode[],
 };
 
-export type WaitForFunctionPolling = number | 'raf';
-
-export type Viewport = {
-  width: number,
-  height: number,
-};
-
-export type ViewportOrNull = null | Viewport;
-
 export type SerializedError = {
   error?: {
     message: string,
@@ -241,7 +227,11 @@ export type BrowserTypeLaunchPersistentContextParams = {
   },
   downloadsPath?: string,
   slowMo?: number,
-  viewport?: ViewportOrNull,
+  noDefaultViewport?: boolean,
+  viewport?: {
+    width: number,
+    height: number,
+  },
   ignoreHTTPSErrors?: boolean,
   javaScriptEnabled?: boolean,
   bypassCSP?: boolean,
@@ -303,7 +293,11 @@ export type BrowserCloseEvent = {};
 export type BrowserCloseParams = {};
 export type BrowserCloseResult = void;
 export type BrowserNewContextParams = {
-  viewport?: ViewportOrNull,
+  noDefaultViewport?: boolean,
+  viewport?: {
+    width: number,
+    height: number,
+  },
   ignoreHTTPSErrors?: boolean,
   javaScriptEnabled?: boolean,
   bypassCSP?: boolean,
@@ -1094,7 +1088,7 @@ export type FrameWaitForFunctionParams = {
   isFunction: boolean,
   arg: SerializedArgument,
   timeout?: number,
-  polling?: WaitForFunctionPolling,
+  pollingInterval?: number,
 };
 export type FrameWaitForFunctionResult = {
   handle: JSHandleChannel,
diff --git a/src/rpc/client/accessibility.ts b/src/rpc/client/accessibility.ts
index ad69d46aec..773ab4e1d3 100644
--- a/src/rpc/client/accessibility.ts
+++ b/src/rpc/client/accessibility.ts
@@ -18,6 +18,7 @@
 import { PageChannel } from '../channels';
 import { ElementHandle } from './elementHandle';
 import * as types from '../../types';
+import { axNodeFromProtocol } from '../serializers';
 
 export class Accessibility {
   private _channel: PageChannel;
@@ -29,6 +30,6 @@ export class Accessibility {
   async snapshot(options: { interestingOnly?: boolean; root?: ElementHandle } = {}): Promise<types.SerializedAXNode | null> {
     const root = options.root ? options.root._elementChannel : undefined;
     const result = await this._channel.accessibilitySnapshot({ interestingOnly: options.interestingOnly, root });
-    return result.rootAXNode || null;
+    return result.rootAXNode ? axNodeFromProtocol(result.rootAXNode) : null;
   }
 }
diff --git a/src/rpc/client/browser.ts b/src/rpc/client/browser.ts
index 6f6decf484..4bf9db4a5c 100644
--- a/src/rpc/client/browser.ts
+++ b/src/rpc/client/browser.ts
@@ -57,6 +57,8 @@ export class Browser extends ChannelOwner<BrowserChannel, BrowserInitializer> {
     return this._wrapApiCall('browser.newContext', async () => {
       const contextOptions: BrowserNewContextParams = {
         ...options,
+        viewport: options.viewport === null ? undefined : options.viewport,
+        noDefaultViewport: options.viewport === null,
         extraHTTPHeaders: options.extraHTTPHeaders ? headersObjectToArray(options.extraHTTPHeaders) : undefined,
       };
       const context = BrowserContext.from((await this._channel.newContext(contextOptions)).context);
diff --git a/src/rpc/client/browserType.ts b/src/rpc/client/browserType.ts
index caa3198980..b0d026be52 100644
--- a/src/rpc/client/browserType.ts
+++ b/src/rpc/client/browserType.ts
@@ -77,6 +77,8 @@ export class BrowserType extends ChannelOwner<BrowserTypeChannel, BrowserTypeIni
     return this._wrapApiCall('browserType.launchPersistentContext', async () => {
       const persistentOptions: BrowserTypeLaunchPersistentContextParams = {
         ...options,
+        viewport: options.viewport === null ? undefined : options.viewport,
+        noDefaultViewport: options.viewport === null,
         ignoreDefaultArgs: Array.isArray(options.ignoreDefaultArgs) ? options.ignoreDefaultArgs : undefined,
         ignoreAllDefaultArgs: !!options.ignoreDefaultArgs && !Array.isArray(options.ignoreDefaultArgs),
         env: options.env ? envObjectToArray(options.env) : undefined,
diff --git a/src/rpc/client/frame.ts b/src/rpc/client/frame.ts
index ea1792b56f..b3f2a4ae8d 100644
--- a/src/rpc/client/frame.ts
+++ b/src/rpc/client/frame.ts
@@ -380,7 +380,13 @@ export class Frame extends ChannelOwner<FrameChannel, FrameInitializer> {
   async waitForFunction<R>(pageFunction: Func1<void, R>, arg?: any, options?: types.WaitForFunctionOptions): Promise<SmartHandle<R>>;
   async waitForFunction<R, Arg>(pageFunction: Func1<Arg, R>, arg: Arg, options: types.WaitForFunctionOptions = {}): Promise<SmartHandle<R>> {
     return this._wrapApiCall(this._apiName('waitForFunction'), async () => {
-      const result = await this._channel.waitForFunction({ expression: String(pageFunction), isFunction: typeof pageFunction === 'function', arg: serializeArgument(arg), ...options });
+      const result = await this._channel.waitForFunction({
+        ...options,
+        pollingInterval: options.polling === 'raf' ? undefined : options.polling,
+        expression: String(pageFunction),
+        isFunction: typeof pageFunction === 'function',
+        arg: serializeArgument(arg),
+      });
       return JSHandle.from(result.handle) as SmartHandle<R>;
     });
   }
diff --git a/src/rpc/protocol.pdl b/src/rpc/protocol.pdl
index 13b95a107a..665c858de1 100644
--- a/src/rpc/protocol.pdl
+++ b/src/rpc/protocol.pdl
@@ -41,24 +41,11 @@ type SerializedArgument
   value: SerializedValue
   handles: Channel[]
 
-union AXNodeValue
-  string
-  number
-
-union AXNodeChecked
-  boolean
-  enum
-    mixed
-
-union AXNodePressed
-  boolean
-  enum
-    mixed
-
 type AXNode
   role: string
   name: string
-  value?: AXNodeValue
+  valueString?: string
+  valueNumber?: number
   description?: string
   keyshortcuts?: string
   roledescription?: string
@@ -72,8 +59,14 @@ type AXNode
   readonly?: boolean
   required?: boolean
   selected?: boolean
-  checked?: AXNodeChecked
-  pressed?: AXNodePressed
+  checked?: enum
+    checked
+    unchecked
+    mixed
+  pressed?: enum
+    pressed
+    released
+    mixed
   level?: number
   valuemin?: number
   valuemax?: number
@@ -83,19 +76,6 @@ type AXNode
   orientation?: string
   children?: AXNode[]
 
-union WaitForFunctionPolling
-  number
-  enum
-    raf
-
-type Viewport
-  width: number
-  height: number
-
-union ViewportOrNull
-  null
-  Viewport
-
 type SerializedError
   error?: object
     message: string
@@ -222,7 +202,10 @@ interface BrowserType
         password?: string
       downloadsPath?: string
       slowMo?: number
-      viewport?: ViewportOrNull
+      noDefaultViewport?: boolean
+      viewport?: object
+        width: number
+        height: number
       ignoreHTTPSErrors?: boolean
       javaScriptEnabled?: boolean
       bypassCSP?: boolean
@@ -270,7 +253,10 @@ interface Browser
 
   command newContext
     parameters
-      viewport?: ViewportOrNull
+      noDefaultViewport?: boolean
+      viewport?: object
+        width: number
+        height: number
       ignoreHTTPSErrors?: boolean
       javaScriptEnabled?: boolean
       bypassCSP?: boolean
@@ -1016,7 +1002,8 @@ interface Frame
       isFunction: boolean
       arg: SerializedArgument
       timeout?: number
-      polling?: WaitForFunctionPolling
+      # When present, polls on interval. Otherwise, polls on raf.
+      pollingInterval?: number
     returns
       handle: JSHandle
 
diff --git a/src/rpc/serializers.ts b/src/rpc/serializers.ts
index 6e738c2845..e4349b6840 100644
--- a/src/rpc/serializers.ts
+++ b/src/rpc/serializers.ts
@@ -21,7 +21,7 @@ import * as util from 'util';
 import { TimeoutError } from '../errors';
 import * as types from '../types';
 import { helper, assert } from '../helper';
-import { SerializedError } from './channels';
+import { SerializedError, AXNode } from './channels';
 import { serializeAsCallArgument, parseEvaluationResultValue } from '../common/utilityScriptSerializers';
 
 export function serializeError(e: any): SerializedError {
@@ -143,3 +143,29 @@ export function envArrayToObject(env: types.EnvArray): types.Env {
     result[name] = value;
   return result;
 }
+
+export function axNodeToProtocol(axNode: types.SerializedAXNode): AXNode {
+  const result: AXNode = {
+    ...axNode,
+    valueNumber: typeof axNode.value === 'number' ? axNode.value : undefined,
+    valueString: typeof axNode.value === 'string' ? axNode.value : undefined,
+    checked: axNode.checked === true ? 'checked' : axNode.checked === false ? 'unchecked' : axNode.checked,
+    pressed: axNode.pressed === true ? 'pressed' : axNode.pressed === false ? 'released' : axNode.pressed,
+    children: axNode.children ? axNode.children.map(axNodeToProtocol) : undefined,
+  };
+  delete (result as any).value;
+  return result;
+}
+
+export function axNodeFromProtocol(axNode: AXNode): types.SerializedAXNode {
+  const result: types.SerializedAXNode = {
+    ...axNode,
+    value: axNode.valueNumber !== undefined ? axNode.valueNumber : axNode.valueString,
+    checked: axNode.checked === 'checked' ? true : axNode.checked === 'unchecked' ? false : axNode.checked,
+    pressed: axNode.pressed === 'pressed' ? true : axNode.pressed === 'released' ? false : axNode.pressed,
+    children: axNode.children ? axNode.children.map(axNodeFromProtocol) : undefined,
+  };
+  delete (result as any).valueNumber;
+  delete (result as any).valueString;
+  return result;
+}
diff --git a/src/rpc/server/browserDispatcher.ts b/src/rpc/server/browserDispatcher.ts
index a5f8aeb06a..caf7321092 100644
--- a/src/rpc/server/browserDispatcher.ts
+++ b/src/rpc/server/browserDispatcher.ts
@@ -37,6 +37,7 @@ export class BrowserDispatcher extends Dispatcher<Browser, BrowserInitializer> i
   async newContext(params: BrowserNewContextParams): Promise<{ context: BrowserContextChannel }> {
     const options = {
       ...params,
+      viewport: params.viewport || (params.noDefaultViewport ? null : undefined),
       extraHTTPHeaders: params.extraHTTPHeaders ? headersArrayToObject(params.extraHTTPHeaders) : undefined,
     };
     return { context: new BrowserContextDispatcher(this._scope, await this._object.newContext(options) as BrowserContextBase) };
diff --git a/src/rpc/server/browserTypeDispatcher.ts b/src/rpc/server/browserTypeDispatcher.ts
index 849183c1ad..9737c38594 100644
--- a/src/rpc/server/browserTypeDispatcher.ts
+++ b/src/rpc/server/browserTypeDispatcher.ts
@@ -46,6 +46,7 @@ export class BrowserTypeDispatcher extends Dispatcher<BrowserType, BrowserTypeIn
   async launchPersistentContext(params: BrowserTypeLaunchPersistentContextParams): Promise<{ context: BrowserContextChannel }> {
     const options = {
       ...params,
+      viewport: params.viewport || (params.noDefaultViewport ? null : undefined),
       ignoreDefaultArgs: params.ignoreAllDefaultArgs ? true : params.ignoreDefaultArgs,
       env: params.env ? envArrayToObject(params.env) : undefined,
       extraHTTPHeaders: params.extraHTTPHeaders ? headersArrayToObject(params.extraHTTPHeaders) : undefined,
diff --git a/src/rpc/server/frameDispatcher.ts b/src/rpc/server/frameDispatcher.ts
index 601eb1997e..3a6d40f2e5 100644
--- a/src/rpc/server/frameDispatcher.ts
+++ b/src/rpc/server/frameDispatcher.ts
@@ -16,7 +16,7 @@
 
 import { Frame, kAddLifecycleEvent, kRemoveLifecycleEvent, kNavigationEvent, NavigationEvent } from '../../frames';
 import * as types from '../../types';
-import { ElementHandleChannel, FrameChannel, FrameInitializer, JSHandleChannel, ResponseChannel, SerializedArgument } from '../channels';
+import { ElementHandleChannel, FrameChannel, FrameInitializer, JSHandleChannel, ResponseChannel, SerializedArgument, FrameWaitForFunctionParams } from '../channels';
 import { Dispatcher, DispatcherScope, lookupNullableDispatcher, existingDispatcher } from './dispatcher';
 import { convertSelectOptionValues, ElementHandleDispatcher, createHandle, convertInputFiles } from './elementHandlerDispatcher';
 import { parseArgument, serializeResult } from './jsHandleDispatcher';
@@ -176,8 +176,12 @@ export class FrameDispatcher extends Dispatcher<Frame, FrameInitializer> impleme
     await this._frame.uncheck(params.selector, params);
   }
 
-  async waitForFunction(params: { expression: string, isFunction: boolean, arg: SerializedArgument } & types.WaitForFunctionOptions): Promise<{ handle: JSHandleChannel }> {
-    return { handle: createHandle(this._scope, await this._frame._waitForFunctionExpression(params.expression, params.isFunction, parseArgument(params.arg), params)) };
+  async waitForFunction(params: FrameWaitForFunctionParams): Promise<{ handle: JSHandleChannel }> {
+    const options = {
+      ...params,
+      polling: params.pollingInterval === undefined ? 'raf' as const : params.pollingInterval
+    };
+    return { handle: createHandle(this._scope, await this._frame._waitForFunctionExpression(params.expression, params.isFunction, parseArgument(params.arg), options)) };
   }
 
   async title(): Promise<{ value: string }> {
diff --git a/src/rpc/server/pageDispatcher.ts b/src/rpc/server/pageDispatcher.ts
index 186c16b146..a0f68f59b5 100644
--- a/src/rpc/server/pageDispatcher.ts
+++ b/src/rpc/server/pageDispatcher.ts
@@ -20,9 +20,9 @@ import { Frame } from '../../frames';
 import { Request } from '../../network';
 import { Page, Worker } from '../../page';
 import * as types from '../../types';
-import { BindingCallChannel, BindingCallInitializer, ElementHandleChannel, PageChannel, PageInitializer, ResponseChannel, WorkerInitializer, WorkerChannel, JSHandleChannel, Binary, SerializedArgument, PagePdfParams, SerializedError } from '../channels';
+import { BindingCallChannel, BindingCallInitializer, ElementHandleChannel, PageChannel, PageInitializer, ResponseChannel, WorkerInitializer, WorkerChannel, JSHandleChannel, Binary, SerializedArgument, PagePdfParams, SerializedError, PageAccessibilitySnapshotResult } from '../channels';
 import { Dispatcher, DispatcherScope, lookupDispatcher, lookupNullableDispatcher } from './dispatcher';
-import { parseError, serializeError, headersArrayToObject } from '../serializers';
+import { parseError, serializeError, headersArrayToObject, axNodeToProtocol } from '../serializers';
 import { ConsoleMessageDispatcher } from './consoleMessageDispatcher';
 import { DialogDispatcher } from './dialogDispatcher';
 import { DownloadDispatcher } from './downloadDispatcher';
@@ -180,12 +180,12 @@ export class PageDispatcher extends Dispatcher<Page, PageInitializer> implements
     await this._page.mouse.click(params.x, params.y, params);
   }
 
-  async accessibilitySnapshot(params: { interestingOnly?: boolean, root?: ElementHandleChannel }): Promise<{ rootAXNode?: types.SerializedAXNode }> {
+  async accessibilitySnapshot(params: { interestingOnly?: boolean, root?: ElementHandleChannel }): Promise<PageAccessibilitySnapshotResult> {
     const rootAXNode = await this._page.accessibility.snapshot({
       interestingOnly: params.interestingOnly,
       root: params.root ? (params.root as ElementHandleDispatcher)._elementHandle : undefined
     });
-    return { rootAXNode: rootAXNode || undefined };
+    return { rootAXNode: rootAXNode ? axNodeToProtocol(rootAXNode) : undefined };
   }
 
   async pdf(params: PagePdfParams): Promise<{ pdf: Binary }> {