Android: not to pause screen capture when Chrome is put to background

content/renderer/render_view_impl.cc

Index: content/renderer/render_view_impl.cc
diff --git a/content/renderer/render_view_impl.cc b/content/renderer/render_view_impl.cc
index 0c57eceedfeb4a5ff928e02c11661de31f1f4558..6e3d0370bd494ca6bca28ec4ed4843b120dc5932 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -84,6 +84,7 @@
 #include "content/renderer/input/input_handler_manager.h"
 #include "content/renderer/internal_document_state_data.h"
 #include "content/renderer/media/audio_device_factory.h"
+#include "content/renderer/media/media_stream_dispatcher.h"
 #include "content/renderer/media/video_capture_impl_manager.h"
 #include "content/renderer/navigation_state_impl.h"
 #include "content/renderer/render_frame_impl.h"
@@ -2277,12 +2278,13 @@ void RenderViewImpl::Close() {
 }
 
 void RenderViewImpl::OnPageWasHidden() {
-#if defined(OS_ANDROID) && BUILDFLAG(ENABLE_WEBRTC)
-  RenderThreadImpl::current()->video_capture_impl_manager()->
-      SuspendDevices(true);
+#if defined(OS_ANDROID)
+  SuspendVideoCaptureDevicesOnPageHidden();
+#if BUILDFLAG(ENABLE_WEBRTC)
   if (speech_recognition_dispatcher_)
     speech_recognition_dispatcher_->AbortAllRecognitions();
 #endif
+#endif
 
   if (webview()) {
     // TODO(lfg): It's not correct to defer the page visibility to the main
@@ -2297,9 +2299,8 @@ void RenderViewImpl::OnPageWasHidden() {
 }
 
 void RenderViewImpl::OnPageWasShown() {
-#if defined(OS_ANDROID) && BUILDFLAG(ENABLE_WEBRTC)
-  RenderThreadImpl::current()->video_capture_impl_manager()->
-      SuspendDevices(false);
+#if defined(OS_ANDROID)
+  ResumeVideoCaptureDevicesOnPageShown();
 #endif
 
   if (webview()) {
@@ -2568,6 +2569,40 @@ bool RenderViewImpl::didTapMultipleTargets(
 
   return handled;
 }
+
+void RenderViewImpl::SuspendVideoCaptureDevicesOnPageHidden() {
+  if (!main_render_frame_)
+    return;
+
+  MediaStreamDispatcher* media_stream_dispatcher =
+      main_render_frame_->GetMediaStreamDispatcher();
+  if (!media_stream_dispatcher)
+    return;
+
+  StreamDeviceInfoArray video_array;
+  media_stream_dispatcher->GetNonScreenCaptureDevices(&video_array);
+  for (const StreamDeviceInfo& device_info : video_array) {
+    RenderThreadImpl::current()->video_capture_impl_manager()->Suspend(
+        device_info.session_id);
+  }
+}
+
+void RenderViewImpl::ResumeVideoCaptureDevicesOnPageShown() {
+  if (!main_render_frame_)
+    return;
+
+  MediaStreamDispatcher* media_stream_dispatcher =
+      main_render_frame_->GetMediaStreamDispatcher();
+  if (!media_stream_dispatcher)
+    return;
+
+  StreamDeviceInfoArray video_array;
+  media_stream_dispatcher->GetNonScreenCaptureDevices(&video_array);
+  for (const StreamDeviceInfo& device_info : video_array) {
+    RenderThreadImpl::current()->video_capture_impl_manager()->Resume(

[miu, 2017/03/24 21:34:13]

Sorry, I didn't realize this in the last round of review: The logic we deleted
from VideoCaptureImplManager tracked whether each device was suspended because
of a "suspend all" operation (on render view hidden), or if it was individually
suspended for some other reason. Devices that are individually suspended should
not be resumed when the "resume all" happens.

For example, the old code handled this case correctly:

1. Code in c/r/m/media_stream_video_capturer_source.cc calls
VideoCaptureImplManager::Suspend() to suspend a device because there are no
consumers of its feed.

2. RenderViewImpl calls VideoCaptureImplManager::SuspendDevices(true) when a
page is hidden. All devices are suspended

3. Once the page is showing again, RenderViewImpl calls
VideoCaptureImplManager::SuspendDevices(false). However, the device suspended in
#1 is NOT resumed. See:
https://cs.chromium.org/chromium/src/content/renderer/media/video_capture_imp...

The current code would resume previously-suspended devices that should remain
suspended because they have no consumers.

+        device_info.session_id);
+  }
+}
 #endif  // defined(OS_ANDROID)
 
 unsigned RenderViewImpl::GetLocalSessionHistoryLengthForTesting() const {