Implement heuristic for showing media controls during playback w/o a mouse

Source/core/html/shadow/MediaControls.cpp

Index: Source/core/html/shadow/MediaControls.cpp
diff --git a/Source/core/html/shadow/MediaControls.cpp b/Source/core/html/shadow/MediaControls.cpp
index 1b1a234275e528d7ea759827b70eb757ce30ff7e..4a4e3cd2a197cd0d34bd7c3bdd0342a8fea0b398 100644
--- a/Source/core/html/shadow/MediaControls.cpp
+++ b/Source/core/html/shadow/MediaControls.cpp
@@ -191,6 +191,11 @@ void MediaControls::show()
     m_panel->show();
 }
 
+void MediaControls::mediaElementFocused()
+{
+    show();

[acolwell GONE FROM CHROMIUM, 2014/05/22 00:31:17]

Should we have a stopHideMediaControlsTimer() call here?

[fs, 2014/05/22 15:48:45]

Probably makes sense. Added.

+}
+
 void MediaControls::hide()
 {
     m_panel->setIsDisplayed(false);
@@ -212,6 +217,16 @@ bool MediaControls::shouldHideMediaControls()
     return !m_panel->hovered();
 }
 
+bool MediaControls::shouldShowMediaControls() const
+{
+    if (m_isMouseOverControls)
+        return true;
+    // Check for 'focus' on the HTMLMediaElement and within the controls/shadow
+    // tree separately (to avoid going through all the potential ancestor hosts
+    // for the focused element.)
+    return mediaElement().focused() || contains(document().focusedElement());
+}
+
 void MediaControls::playbackStarted()
 {
     m_currentTimeDisplay->show();
@@ -229,7 +244,7 @@ void MediaControls::playbackProgressed()
     m_timeline->setPosition(mediaElement().currentTime());
     updateCurrentTimeDisplay();
 
-    if (!m_isMouseOverControls && mediaElement().hasVideo())
+    if (mediaElement().hasVideo() && !shouldShowMediaControls())

[acolwell GONE FROM CHROMIUM, 2014/05/22 00:31:17]

!shouldShowMediaControls() conceptually seems like it should be equivalent to
shouldHideMediaControls(). Can we combine these into 1 function somehow so
different code paths don't end up disagreeing on whether the controls should be
visible or not? 

Also FYI https://codereview.chromium.org/296743007/ adds the hasVideo()
condition to shouldHideMediaControls() so that is one less check you'll have to
do here.

[fs, 2014/05/22 15:48:45]

I integrated should_Show_MediaControls in should_Hide_MediaControls (dropping
the hasVideo() check here per below).
 
I added that bit here, and will rebase and fix up as needed.

         makeTransparent();
 }