Hook up Android closed captions 'enabled' setting to Blink

Source/core/html/HTMLMediaElement.cpp

Index: Source/core/html/HTMLMediaElement.cpp
diff --git a/Source/core/html/HTMLMediaElement.cpp b/Source/core/html/HTMLMediaElement.cpp
index 5558692f2650d0baa1f5ee8941d302f798161f0d..61bf3b111bd6d4a29ce44ec4131243ce3784476f 100644
--- a/Source/core/html/HTMLMediaElement.cpp
+++ b/Source/core/html/HTMLMediaElement.cpp
@@ -375,6 +375,13 @@ HTMLMediaElement::HTMLMediaElement(const QualifiedName& tagName, Document& docum
 
     setHasCustomStyleCallbacks();
     addElementToDocumentMap(this, &document);
+    document.registerForTextTracksVisibilityChangedCallback(this);
+#if OS(ANDROID)

[tkent, 2015/04/29 23:58:44]

Can you set the default value of textTracksEnabled "true", and avoid |#if
OS(ANDROID)|?

[srivats, 2015/05/01 23:03:31]

Doing that will have closed captions turned on by default for videos with tracks
on all platforms and also breaks some media layout tests.

+    // The OS setting for closed captions state is only available on Android, iOS
+    // and OSX. Set closed captions visibility based on OS text tracks state only if the platform
+    // is Android because the setting is currently only plumbed down on Android.
+    setClosedCaptionsVisible(document.settings()->textTracksEnabled());

[tkent, 2015/04/29 23:58:44]

document.settings() can be NULL.

[srivats, 2015/05/01 23:03:31]

Done.

+#endif
 }
 
 HTMLMediaElement::~HTMLMediaElement()
@@ -413,6 +420,8 @@ HTMLMediaElement::~HTMLMediaElement()
     }
 #endif
 
+    document().unregisterFromTextTracksVisibilityChangedCallback(this);
+
 #if ENABLE(OILPAN)
     if (m_closeMediaSourceWhenFinalizing)
         closeMediaSource();
@@ -3397,7 +3406,13 @@ void HTMLMediaElement::configureTextTrackDisplay(VisibilityChangeAssumption assu
         return;
     }
     m_haveVisibleTextTrack = haveVisibleTextTrack;
+#if !OS(ANDROID)
     m_closedCaptionsVisible = m_haveVisibleTextTrack;
+#else
+    // Set closed captions visible during initial load only if the video has a
+    // visible text track and when the android platform closed captions are enabled.
+    m_closedCaptionsVisible = m_haveVisibleTextTrack && document().settings()->textTracksEnabled();
+#endif
 
     if (!m_haveVisibleTextTrack && !mediaControls())
         return;