Add MediaStreamSource frame rate calculation to the tracker.

content/browser/renderer_host/media/video_capture_controller.cc

Index: content/browser/renderer_host/media/video_capture_controller.cc
diff --git a/content/browser/renderer_host/media/video_capture_controller.cc b/content/browser/renderer_host/media/video_capture_controller.cc
index 4b6d4b94b1e0fca3c3d4827a4c0bb200130f42ea..deecf3b999bc2bb0f2ad6e61bcd6666d4ae934cb 100644
--- a/content/browser/renderer_host/media/video_capture_controller.cc
+++ b/content/browser/renderer_host/media/video_capture_controller.cc
@@ -179,6 +179,9 @@ class VideoCaptureController::VideoCaptureDeviceClient
 
   // The pool of shared-memory buffers used for capturing.
   const scoped_refptr<VideoCaptureBufferPool> buffer_pool_;
+
+  // Number of frames dropped due to that no shared buffers are available.
+  int frames_dropped_;
 };
 
 VideoCaptureController::VideoCaptureController(int max_buffers)
@@ -191,7 +194,7 @@ VideoCaptureController::VideoCaptureController(int max_buffers)
 VideoCaptureController::VideoCaptureDeviceClient::VideoCaptureDeviceClient(
     const base::WeakPtr<VideoCaptureController>& controller,
     const scoped_refptr<VideoCaptureBufferPool>& buffer_pool)
-    : controller_(controller), buffer_pool_(buffer_pool) {}
+    : controller_(controller), buffer_pool_(buffer_pool), frames_dropped_(0) {}
 
 VideoCaptureController::VideoCaptureDeviceClient::~VideoCaptureDeviceClient() {}
 
@@ -365,8 +368,11 @@ void VideoCaptureController::VideoCaptureDeviceClient::OnIncomingCapturedData(
   scoped_refptr<Buffer> buffer =
       DoReserveOutputBuffer(media::VideoFrame::I420, dimensions);
 
-  if (!buffer.get())
+  if (!buffer.get()) {
+    ++frames_dropped_;
     return;
+  }
+
   uint8* yplane = NULL;
   bool flip = false;
   yplane = reinterpret_cast<uint8*>(buffer->data());
@@ -468,6 +474,7 @@ void VideoCaptureController::VideoCaptureDeviceClient::OnIncomingCapturedData(
 
   VideoCaptureFormat format(
       dimensions, frame_format.frame_rate, media::PIXEL_FORMAT_I420);
+  format.number_of_dropped_frames = frames_dropped_;
   BrowserThread::PostTask(
       BrowserThread::IO,
       FROM_HERE,