Implement screen capture for android

content/browser/media/capture/desktop_capture_device.cc

Index: content/browser/media/capture/desktop_capture_device.cc
diff --git a/content/browser/media/capture/desktop_capture_device.cc b/content/browser/media/capture/desktop_capture_device.cc
index a11e473e83cf6497e49952e5c594ad88a317100a..ef44f56b15ffb90d311774d1bcda34ece27c017a 100644
--- a/content/browser/media/capture/desktop_capture_device.cc
+++ b/content/browser/media/capture/desktop_capture_device.cc
@@ -17,6 +17,9 @@
 #include "content/public/browser/desktop_media_id.h"
 #include "content/public/browser/power_save_blocker.h"
 #include "media/base/video_util.h"
+#if defined(OS_ANDROID)
+#include "media/screen_capture/android/screen_capturer_android.h"
+#endif
 #include "third_party/libyuv/include/libyuv/scale_argb.h"
 #include "third_party/webrtc/modules/desktop_capture/cropping_window_capturer.h"
 #include "third_party/webrtc/modules/desktop_capture/desktop_and_cursor_composer.h"
@@ -182,6 +185,13 @@ void DesktopCaptureDevice::Core::AllocateAndStart(
 
   desktop_capturer_->Start(this);
 
+#if defined(OS_ANDROID)
+  // For android, we don't use capture_timer_ to triger capturing. Instead,
+  // we use ImageReader.OnImageAvailableListener to listen when a screen frame
+  // available which is similar with VideoCapture

[miu, 2015/05/20 03:33:27]

What happens if the screen does not update for a long while?  Will this stop the
providing frames?

The comment here explains the issue that affects tab capture on all platforms,
and also desktop capture on ChromeOS:
https://code.google.com/p/chromium/codesearch#chromium/src/content/browser/me...

+  return;
+#endif
+
   CaptureFrameAndScheduleNext();
 }
 
@@ -199,8 +209,10 @@ DesktopCaptureDevice::Core::CreateSharedMemory(size_t size) {
 
 void DesktopCaptureDevice::Core::OnCaptureCompleted(
     webrtc::DesktopFrame* frame) {
+#if !defined(OS_ANDROID)

[miu, 2015/05/20 03:33:27]

Why don't these statements apply to the android platform?  At the least, provide
a comment here.

   DCHECK(task_runner_->BelongsToCurrentThread());
   DCHECK(capture_in_progress_);
+#endif
 
   if (!first_capture_returned_) {
     first_capture_returned_ = true;
@@ -410,8 +422,13 @@ scoped_ptr<media::VideoCaptureDevice> DesktopCaptureDevice::Create(
 
   switch (source.type) {
     case DesktopMediaID::TYPE_SCREEN: {
+#if defined(OS_ANDROID)
+      scoped_ptr<webrtc::ScreenCapturer> screen_capturer(
+          new media::ScreenCapturerAndroid());
+#else
       scoped_ptr<webrtc::ScreenCapturer> screen_capturer(
           webrtc::ScreenCapturer::Create(options));
+#endif
       if (screen_capturer && screen_capturer->SelectScreen(source.id)) {
         capturer.reset(new webrtc::DesktopAndCursorComposer(
             screen_capturer.release(),