Adds UMA histograms for desktop tab and audio capture through

content/browser/media/capture/web_contents_video_capture_device.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_MEDIA_CAPTURE_WEB_CONTENTS_VIDEO_CAPTURE_DEVICE_H_
 #define CONTENT_BROWSER_MEDIA_CAPTURE_WEB_CONTENTS_VIDEO_CAPTURE_DEVICE_H_
 
 #include <string>
 
 #include "base/macros.h"
@@ skipping 10 matching lines @@
 //
 // An instance is created by providing a device_id.  The device_id contains
 // information necessary for finding a WebContents instance.  From then on,
 // WebContentsVideoCaptureDevice will capture from the RenderWidgetHost that
 // encompasses the currently active RenderFrameHost tree for that that
 // WebContents instance.  As the RenderFrameHost tree mutates (e.g., due to page
 // navigations, or crashes/reloads), capture will continue without interruption.
 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;
 
   // VideoCaptureDevice implementation.
   void AllocateAndStart(const media::VideoCaptureParams& params,
                         scoped_ptr<Client> client) override;
   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_;
 
   DISALLOW_COPY_AND_ASSIGN(WebContentsVideoCaptureDevice);
 };
 
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_MEDIA_CAPTURE_WEB_CONTENTS_VIDEO_CAPTURE_DEVICE_H_