Bug 923133 - Remove unneeded main thread GL context management in -[ChildView lockFocus]. r=mattwoodrow

--HG--
extra : rebase_source : 5098476ad30f13f2ea99e91ed0120b535ae53e78

widget/cocoa/nsChildView.h

@@ -323,7 +323,6 @@ typedef NSInteger NSEventGestureAxis;
                              type:(mozilla::WidgetMouseEvent::exitType)aType;
 
 - (void)update;
-- (void)lockFocus;
 - (void) _surfaceNeedsUpdate:(NSNotification*)notification;
 
 - (BOOL)isPluginView;

widget/cocoa/nsChildView.mm

@@ -3229,23 +3229,6 @@ NSEvent* gLastDragMouseDownEvent = nil;
   return [[self window] isMovableByWindowBackground];
 }
 
-- (void)lockFocus
-{
-  NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
-
-  [super lockFocus];
-
-  if (mGLContext) {
-    if ([mGLContext view] != self) {
-      [mGLContext setView:self];
-    }
-
-    [mGLContext makeCurrentContext];
-  }
-
-  NS_OBJC_END_TRY_ABORT_BLOCK;
-}
-
 -(void)update
 {
   if (mGLContext) {