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

content/child/blink_platform_impl.cc

Index: content/child/blink_platform_impl.cc
diff --git a/content/child/blink_platform_impl.cc b/content/child/blink_platform_impl.cc
index 0b41bff1199ca0e08cb56193556e4d79a0bf3cbe..c3f33ee874b9ee70a33929ba162741f28c3ff145 100644
--- a/content/child/blink_platform_impl.cc
+++ b/content/child/blink_platform_impl.cc
@@ -737,6 +737,11 @@ blink::WebPushProvider* BlinkPlatformImpl::pushProvider() {
   return PushProvider::ThreadSpecificInstance(main_thread_task_runner_);
 }
 
+blink::WebMediaCapabilitiesClient*
+BlinkPlatformImpl::mediaCapabilitiesClient() {
+  return &media_capabilities_client_;
+}
+
 WebThemeEngine* BlinkPlatformImpl::themeEngine() {
   return &native_theme_engine_;
 }