Media Controls: make the MediaControlsOverlayPlayButton a runtime enabled flag.

content/child/runtime_features.cc

Index: content/child/runtime_features.cc
diff --git a/content/child/runtime_features.cc b/content/child/runtime_features.cc
index c4073ed116e8788728fd06978e1cab55b46df30b..60298d5e37abcc44349f65b25343bbe664f9adb3 100644
--- a/content/child/runtime_features.cc
+++ b/content/child/runtime_features.cc
@@ -26,7 +26,7 @@ namespace content {
 static void SetRuntimeFeatureDefaultsForPlatform() {
 #if defined(OS_ANDROID)
   // Android does not have support for PagePopup
-  WebRuntimeFeatures::enablePagePopup(false);
+  WebRuntimeFeatures::enablePagePopupa(false);
   // No plan to support complex UI for date/time INPUT types.
   WebRuntimeFeatures::enableInputMultipleFieldsUI(false);
   // Android does not yet support SharedWorker. crbug.com/154571
@@ -45,6 +45,7 @@ static void SetRuntimeFeatureDefaultsForPlatform() {
   // Android does not yet support SystemMonitor.
   WebRuntimeFeatures::enableOnDeviceChange(false);
   WebRuntimeFeatures::enableMediaSession(true);
+  WebRuntimeFeatures::enableMediaControlsOverlayPlayButton(true);
 #else  // defined(OS_ANDROID)
   WebRuntimeFeatures::enableNavigatorContentUtils(true);
   if (base::FeatureList::IsEnabled(