diff --git a/browser_patches/firefox/BUILD_NUMBER b/browser_patches/firefox/BUILD_NUMBER
index 8cea824fe8..0d1f9f219f 100644
--- a/browser_patches/firefox/BUILD_NUMBER
+++ b/browser_patches/firefox/BUILD_NUMBER
@@ -1,2 +1,2 @@
-1190
-Changed: joel.einbinder@gmail.com Tue 13 Oct 2020 09:08:57 AM PDT
+1191
+Changed: yurys@chromium.org Wed Oct 14 16:12:19 PDT 2020
diff --git a/browser_patches/firefox/juggler/protocol/PageHandler.js b/browser_patches/firefox/juggler/protocol/PageHandler.js
index 5feb2ae733..201e07b7ae 100644
--- a/browser_patches/firefox/juggler/protocol/PageHandler.js
+++ b/browser_patches/firefox/juggler/protocol/PageHandler.js
@@ -121,7 +121,7 @@ class PageHandler {
 
   _onScreencastStarted() {
     const info = this._pageTarget.screencastInfo();
-    this._session.emitEvent('Page.screencastStarted', { screencastId: '' + info.videoSessionId, file: info.file });
+    this._session.emitEvent('Page.screencastStarted', { screencastId: info.videoSessionId, file: info.file });
   }
 
   _onDialogOpened(dialog) {
diff --git a/browser_patches/firefox/juggler/screencast/nsIScreencastService.idl b/browser_patches/firefox/juggler/screencast/nsIScreencastService.idl
index acac1bd3bd..d3a82a7cda 100644
--- a/browser_patches/firefox/juggler/screencast/nsIScreencastService.idl
+++ b/browser_patches/firefox/juggler/screencast/nsIScreencastService.idl
@@ -12,10 +12,10 @@ interface nsIDocShell;
 [scriptable, uuid(d8c4d9e0-9462-445e-9e43-68d3872ad1de)]
 interface nsIScreencastService : nsISupports
 {
-  long startVideoRecording(in nsIDocShell docShell, in ACString fileName, in uint32_t width, in uint32_t height, in double scale, in int32_t offset_top);
+  AString startVideoRecording(in nsIDocShell docShell, in ACString fileName, in uint32_t width, in uint32_t height, in double scale, in int32_t offset_top);
 
   /**
    * Will emit 'juggler-screencast-stopped' when the video file is saved.
    */
-  void stopVideoRecording(in long sessionId);
+  void stopVideoRecording(in AString sessionId);
 };
diff --git a/browser_patches/firefox/juggler/screencast/nsScreencastService.cpp b/browser_patches/firefox/juggler/screencast/nsScreencastService.cpp
index e4b6fadf86..c4923eba35 100644
--- a/browser_patches/firefox/juggler/screencast/nsScreencastService.cpp
+++ b/browser_patches/firefox/juggler/screencast/nsScreencastService.cpp
@@ -12,6 +12,7 @@
 #include "mozilla/StaticPtr.h"
 #include "nsIDocShell.h"
 #include "nsIObserverService.h"
+#include "nsIRandomGenerator.h"
 #include "nsISupportsPrimitives.h"
 #include "nsThreadManager.h"
 #include "nsView.h"
@@ -34,7 +35,7 @@ namespace {
 
 StaticRefPtr<nsScreencastService> gScreencastService;
 
-rtc::scoped_refptr<webrtc::VideoCaptureModule> CreateWindowCapturer(nsIWidget* widget, int sessionId) {
+rtc::scoped_refptr<webrtc::VideoCaptureModule> CreateWindowCapturer(nsIWidget* widget) {
   if (gfxPlatform::IsHeadless()) {
     HeadlessWidget* headlessWidget = static_cast<HeadlessWidget*>(widget);
     return HeadlessWindowCapturer::Create(headlessWidget);
@@ -47,19 +48,35 @@ rtc::scoped_refptr<webrtc::VideoCaptureModule> CreateWindowCapturer(nsIWidget* w
   nsCString windowId;
   windowId.AppendPrintf("%" PRIuPTR, rawWindowId);
   bool captureCursor = false;
-  return webrtc::DesktopCaptureImpl::Create(sessionId, windowId.get(), webrtc::CaptureDeviceType::Window, captureCursor);
+  static int moduleId = 0;
+  return webrtc::DesktopCaptureImpl::Create(++moduleId, windowId.get(), webrtc::CaptureDeviceType::Window, captureCursor);
 }
 
-void NotifyScreencastStopped(int32_t sessionId) {
+void NotifyScreencastStopped(const nsString& sessionId) {
   nsCOMPtr<nsIObserverService> observerService = mozilla::services::GetObserverService();
   if (!observerService) {
     fprintf(stderr, "NotifyScreencastStopped error: no observer service\n");
     return;
   }
 
-  nsString id;
-  id.AppendPrintf("%" PRIi32, sessionId);
-  observerService->NotifyObservers(nullptr, "juggler-screencast-stopped", id.get());
+  observerService->NotifyObservers(nullptr, "juggler-screencast-stopped", sessionId.get());
+}
+
+nsresult generateUid(nsString& uid) {
+  nsresult rv = NS_OK;
+  nsCOMPtr<nsIRandomGenerator> rg = do_GetService("@mozilla.org/security/random-generator;1", &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  uint8_t* buffer;
+  const int kLen = 16;
+  rv = rg->GenerateRandomBytes(kLen, &buffer);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  for (int i = 0; i < kLen; i++) {
+    uid.AppendPrintf("%" PRIx8, buffer[i]);
+  }
+  free(buffer);
+  return rv;
 }
 }
 
@@ -123,9 +140,8 @@ nsScreencastService::nsScreencastService() = default;
 nsScreencastService::~nsScreencastService() {
 }
 
-nsresult nsScreencastService::StartVideoRecording(nsIDocShell* aDocShell, const nsACString& aFileName, uint32_t width, uint32_t height, double scale, int32_t offsetTop, int32_t* sessionId) {
+nsresult nsScreencastService::StartVideoRecording(nsIDocShell* aDocShell, const nsACString& aFileName, uint32_t width, uint32_t height, double scale, int32_t offsetTop, nsAString& sessionId) {
   MOZ_RELEASE_ASSERT(NS_IsMainThread(), "Screencast service must be started on the Main thread.");
-  *sessionId = -1;
 
   PresShell* presShell = aDocShell->GetPresShell();
   if (!presShell)
@@ -138,8 +154,7 @@ nsresult nsScreencastService::StartVideoRecording(nsIDocShell* aDocShell, const
     return NS_ERROR_UNEXPECTED;
   nsIWidget* widget = view->GetWidget();
 
-  *sessionId = ++mLastSessionId;
-  rtc::scoped_refptr<webrtc::VideoCaptureModule> capturer = CreateWindowCapturer(widget, *sessionId);
+  rtc::scoped_refptr<webrtc::VideoCaptureModule> capturer = CreateWindowCapturer(widget);
   if (!capturer)
     return NS_ERROR_FAILURE;
 
@@ -171,11 +186,17 @@ nsresult nsScreencastService::StartVideoRecording(nsIDocShell* aDocShell, const
   if (!session->Start())
     return NS_ERROR_FAILURE;
 
-  mIdToSession.emplace(*sessionId, std::move(session));
+  nsString uid;
+  nsresult rv = generateUid(uid);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  sessionId = uid;
+  mIdToSession.emplace(uid, std::move(session));
   return NS_OK;
 }
 
-nsresult nsScreencastService::StopVideoRecording(int32_t sessionId) {
+nsresult nsScreencastService::StopVideoRecording(const nsAString& aSessionId) {
+  nsString sessionId(aSessionId);
   auto it = mIdToSession.find(sessionId);
   if (it == mIdToSession.end())
     return NS_ERROR_INVALID_ARG;
diff --git a/browser_patches/firefox/juggler/screencast/nsScreencastService.h b/browser_patches/firefox/juggler/screencast/nsScreencastService.h
index c9df1a1138..082416ca74 100644
--- a/browser_patches/firefox/juggler/screencast/nsScreencastService.h
+++ b/browser_patches/firefox/juggler/screencast/nsScreencastService.h
@@ -5,7 +5,7 @@
 #pragma once
 
 #include <memory>
-#include <unordered_map>
+#include <map>
 #include "nsIScreencastService.h"
 
 namespace mozilla {
@@ -23,8 +23,7 @@ class nsScreencastService final : public nsIScreencastService {
   ~nsScreencastService();
 
   class Session;
-  int mLastSessionId = 0;
-  std::unordered_map<int, std::unique_ptr<Session>> mIdToSession;
+  std::map<nsString, std::unique_ptr<Session>> mIdToSession;
 };
 
 }  // namespace mozilla