Make scrubbing a MediaControls-internal concept

Source/core/html/shadow/MediaControlElements.cpp

Index: Source/core/html/shadow/MediaControlElements.cpp
diff --git a/Source/core/html/shadow/MediaControlElements.cpp b/Source/core/html/shadow/MediaControlElements.cpp
index 80337bca6c90573670c4b7f91d4d5934fb3f285c..d082c9bf30ae1c0998455d3b125c32f3ac4f72ce 100644
--- a/Source/core/html/shadow/MediaControlElements.cpp
+++ b/Source/core/html/shadow/MediaControlElements.cpp
@@ -358,18 +358,17 @@ PassRefPtr<MediaControlTimelineElement> MediaControlTimelineElement::create(Medi
 
 void MediaControlTimelineElement::defaultEventHandler(Event* event)
 {
-    // Left button is 0. Rejects mouse events not from left button.
-    if (event->isMouseEvent() && toMouseEvent(event)->button())
+    if (event->isMouseEvent() && toMouseEvent(event)->button() != LeftButton)
         return;
 
     if (!inDocument() || !document().isActive())
         return;
 
     if (event->type() == EventTypeNames::mousedown)
-        mediaControllerInterface().beginScrubbing();
+        mediaControls().beginScrubbing();
 
     if (event->type() == EventTypeNames::mouseup)
-        mediaControllerInterface().endScrubbing();
+        mediaControls().endScrubbing();
 
     MediaControlInputElement::defaultEventHandler(event);