Media Controls: don't activate buttons when tapping on hidden controls.

third_party/WebKit/LayoutTests/media/media-controls.js

 var captionsButtonElement;
 var captionsButtonCoordinates;
 
 // As specified in mediaControls.css, this is how long it takes to fade out controls
 const controlsFadeOutDurationMs = 300;
 
 // The timeout for the hide-after-no-mouse-movement behavior. Defined (and
 // should mirror) the value 'timeWithoutMouseMovementBeforeHidingMediaControls'
 // in MediaControls.cpp.
 const controlsMouseMovementTimeoutMs = 3000;
@@ skipping 162 matching lines @@
         throw "The media will end before the controls have been hidden";
 
     setTimeout(func, hideTimeoutMs);
 }
 
 function hasFullscreenButton(element)
 {
     var size = mediaControlsButtonDimensions(element, "fullscreen-button");
     return size[0] > 0 && size[1] > 0;
 }
+
+function isControlsPanelVisible(element)
+{
+    return getComputedStyle(mediaControlsButton(element, "panel")).opacity == "1";
+}