Notify WebMediaPlayer when its ancestor enters/exists fullscreen.

third_party/WebKit/Source/web/FrameLoaderClientImpl.cpp

Index: third_party/WebKit/Source/web/FrameLoaderClientImpl.cpp
diff --git a/third_party/WebKit/Source/web/FrameLoaderClientImpl.cpp b/third_party/WebKit/Source/web/FrameLoaderClientImpl.cpp
index db1de678cac7e8bda77e43567030f9960c02da88..463f2280aaf5ebe4293f79b581b30f4112df2ee6 100644
--- a/third_party/WebKit/Source/web/FrameLoaderClientImpl.cpp
+++ b/third_party/WebKit/Source/web/FrameLoaderClientImpl.cpp
@@ -787,9 +787,28 @@ std::unique_ptr<WebMediaPlayer> FrameLoaderClientImpl::createWebMediaPlayer(
   HTMLMediaElementEncryptedMedia& encryptedMedia =
       HTMLMediaElementEncryptedMedia::from(htmlMediaElement);
   WebString sinkId(HTMLMediaElementAudioOutputDevice::sinkId(htmlMediaElement));
-  return wrapUnique(webFrame->client()->createMediaPlayer(
-      source, client, &encryptedMedia, encryptedMedia.contentDecryptionModule(),
-      sinkId));
+  std::unique_ptr<WebMediaPlayer> mediaPlayer =
+      wrapUnique(webFrame->client()->createMediaPlayer(
+          source, client, &encryptedMedia,
+          encryptedMedia.contentDecryptionModule(), sinkId));
+
+  // Notify WebMediaPlayer: if the current media is active fullscreen element;
+  // or is a descendant of the fullscreen element and covers most of the window.
+  Element* fullscreenElement =
+      Fullscreen::currentFullScreenElementFrom(htmlMediaElement.document());
+  if (fullscreenElement == htmlMediaElement) {
+    mediaPlayer->enteredFullscreen();
+  } else if (fullscreenElement &&
+             fullscreenElement->isShadowIncludingInclusiveAncestorOf(
+                 &htmlMediaElement) &&
+             htmlMediaElement.clientWidth() >=
+                 htmlMediaElement.document().domWindow()->innerWidth() * 0.9 &&
+             htmlMediaElement.clientHeight() >=
+                 htmlMediaElement.document().domWindow()->innerHeight() * 0.9) {
+    mediaPlayer->enteredFullWindow();
+  }
+
+  return mediaPlayer;
 }
 
 ObjectContentType FrameLoaderClientImpl::getObjectContentType(