Media Capabilities: add plumbing between Blink and media/blink/.

third_party/WebKit/public/platform/Platform.h

Index: third_party/WebKit/public/platform/Platform.h
diff --git a/third_party/WebKit/public/platform/Platform.h b/third_party/WebKit/public/platform/Platform.h
index 9b20ac06bada87bb651c29bc058b0d7df0cc5518..b50e7057f3582a5052e9d6468ff9218c0a24ee3c 100644
--- a/third_party/WebKit/public/platform/Platform.h
+++ b/third_party/WebKit/public/platform/Platform.h
@@ -92,6 +92,7 @@ class WebIDBFactory;
 class WebImageCaptureFrameGrabber;
 class WebMIDIAccessor;
 class WebMIDIAccessorClient;
+class WebMediaCapabilitiesClient;
 class WebMediaPlayer;
 class WebMediaRecorderHandler;
 class WebMediaStream;
@@ -677,6 +678,12 @@ class BLINK_PLATFORM_EXPORT Platform {
 
   virtual WebTrialTokenValidator* trialTokenValidator() { return nullptr; }
 
+  // Media Capabilities --------------------------------------------------
+
+  virtual WebMediaCapabilitiesClient* mediaCapabilitiesClient() {
+    return nullptr;
+  }
+
   // Memory ------------------------------------------------------------
 
   // Requests purging memory. The platform may or may not purge memory,