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

content/child/blink_platform_impl.h

Index: content/child/blink_platform_impl.h
diff --git a/content/child/blink_platform_impl.h b/content/child/blink_platform_impl.h
index bd33f51eedf36f193a542417a9daabcbd4717e7b..4483c90d07bd052b4935ba2b6349145ac8a4a4ff 100644
--- a/content/child/blink_platform_impl.h
+++ b/content/child/blink_platform_impl.h
@@ -16,6 +16,7 @@
 #include "components/webcrypto/webcrypto_impl.h"
 #include "content/child/webfallbackthemeengine_impl.h"
 #include "content/common/content_export.h"
+#include "media/blink/webmediacapabilitiesclient_impl.h"
 #include "third_party/WebKit/public/platform/Platform.h"
 #include "third_party/WebKit/public/platform/WebGestureDevice.h"
 #include "third_party/WebKit/public/platform/WebURLError.h"
@@ -110,6 +111,7 @@ class CONTENT_EXPORT BlinkPlatformImpl
   blink::WebCrypto* crypto() override;
   blink::WebNotificationManager* notificationManager() override;
   blink::WebPushProvider* pushProvider() override;
+  blink::WebMediaCapabilitiesClient* mediaCapabilitiesClient() override;
 
   blink::WebString domCodeStringFromEnum(int dom_code) override;
   int domEnumFromCodeString(const blink::WebString& codeString) override;
@@ -142,6 +144,7 @@ class CONTENT_EXPORT BlinkPlatformImpl
   WebFallbackThemeEngineImpl fallback_theme_engine_;
   base::ThreadLocalStorage::Slot current_thread_slot_;
   webcrypto::WebCryptoImpl web_crypto_;
+  media::WebMediaCapabilitiesClientImpl media_capabilities_client_;
 
   scoped_refptr<ThreadSafeSender> thread_safe_sender_;
   scoped_refptr<NotificationDispatcher> notification_dispatcher_;