Adds UMA histograms for desktop tab and audio capture through

content/browser/media/capture/web_contents_video_capture_device.h

Index: content/browser/media/capture/web_contents_video_capture_device.h
diff --git a/content/browser/media/capture/web_contents_video_capture_device.h b/content/browser/media/capture/web_contents_video_capture_device.h
index ab0e03ad7d4d5ffa89c4cdb7d6ab35f30f49cbd4..d8576b55b1caa23744c0273b7bbbae3e00991b09 100644
--- a/content/browser/media/capture/web_contents_video_capture_device.h
+++ b/content/browser/media/capture/web_contents_video_capture_device.h
@@ -28,9 +28,16 @@ namespace content {
 class CONTENT_EXPORT WebContentsVideoCaptureDevice
     : public media::VideoCaptureDevice {
  public:
+  enum JavaScriptType {

[miu, 2016/03/24 20:51:03]

This is an abstraction violation.  There's no reason the WCVCD should care about
the JavaScript API that was being used when creating it.

Instead, please do these UMAs in the render process, preferably in the code
modules specific to each API.  Also, it's worth considering whether you really
need to do this at all.  Meaning, do you really need a UMA for the first frame? 
Why isn't it enough to just have a UMA when the capture device is created (in
VideoCaptureManager)?  What will this information be used for?

[GeorgeZ, 2016/03/25 16:35:04]

Thanks for pointing this out.

I was asked to mimic UMAs for desktop screen and window captures where they put
UMAs for first frame.

I will revert all the changes in the this class and add a UMA in
VideoCaptureManager.
 

+    CHROME_TAB_CAPTURE,
+    CHROME_CHOOSE_DESKTOP_MEDIA,
+    NONE_TYPE
+  };
+
   // Create a WebContentsVideoCaptureDevice instance from the given
   // |device_id|.  Returns NULL if |device_id| is invalid.
-  static media::VideoCaptureDevice* Create(const std::string& device_id);
+  static media::VideoCaptureDevice* Create(const std::string& device_id,
+                                           JavaScriptType type);
 
   ~WebContentsVideoCaptureDevice() override;
 
@@ -40,10 +47,10 @@ class CONTENT_EXPORT WebContentsVideoCaptureDevice
   void StopAndDeAllocate() override;
 
  private:
-  WebContentsVideoCaptureDevice(
-      int render_process_id,
-      int main_render_frame_id,
-      bool enable_auto_throttling);
+  WebContentsVideoCaptureDevice(int render_process_id,
+                                int main_render_frame_id,
+                                bool enable_auto_throttling,
+                                JavaScriptType type);
 
   const scoped_ptr<media::ScreenCaptureDeviceCore> core_;