Add IPC to query capabilities of video input devices.

content/browser/frame_host/render_frame_host_delegate.h

Index: content/browser/frame_host/render_frame_host_delegate.h
diff --git a/content/browser/frame_host/render_frame_host_delegate.h b/content/browser/frame_host/render_frame_host_delegate.h
index 4f3178036cda45d6dee1f0b9e6f4d0bbd2672ad9..be80f52bbf0a49b4a905578f80599589ddaf0cad 100644
--- a/content/browser/frame_host/render_frame_host_delegate.h
+++ b/content/browser/frame_host/render_frame_host_delegate.h
@@ -158,6 +158,11 @@ class CONTENT_EXPORT RenderFrameHostDelegate {
   virtual bool CheckMediaAccessPermission(const GURL& security_origin,

[dcheng, 2017/01/20 07:56:50]

It's not introduced by this CL, but please add a TODO and file a bug to use
url::Origin here rather than GURL.

[Guido Urdaneta, 2017/01/20 12:40:58]

Done.

                                           MediaStreamType type);
 
+  // Returns the ID of the default device for the given media device |type|.
+  // If the returned value is an empty string, it means that there is no
+  // default device for the given |type|.
+  virtual std::string GetDefaultMediaDeviceID(MediaStreamType type);
+
   // Get the accessibility mode for the WebContents that owns this frame.
   virtual AccessibilityMode GetAccessibilityMode() const;