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 11a87ad90852e57c05e4e348eb7bec87bf1d63c7..ef9e414f107dfd3ea03de3620b4dd713292d7ab9 100644
--- a/Source/core/html/shadow/MediaControlElements.cpp
+++ b/Source/core/html/shadow/MediaControlElements.cpp
@@ -456,18 +456,17 @@ 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);