--- a/widget/cocoa/nsChildView.h
+++ b/widget/cocoa/nsChildView.h
@@ -200,16 +200,20 @@ typedef NSInteger NSEventGestureAxis;
   BOOL mPendingFullDisplay;
   BOOL mPendingDisplay;
 
   // WheelStart/Stop events should always come in pairs. This BOOL records the
   // last received event so that, when we receive one of the events, we make sure
   // to send its pair event first, in case we didn't yet for any reason.
   BOOL mExpectingWheelStop;
 
+  // Set to YES when our GL surface has been updated and we need to call
+  // updateGLContext before we composite.
+  BOOL mNeedsGLUpdate;
+
   // Holds our drag service across multiple drag calls. The reference to the
   // service is obtained when the mouse enters the view and is released when
   // the mouse exits or there is a drop. This prevents us from having to
   // re-establish the connection to the service manager many times per second
   // when handling |draggingUpdated:| messages.
   nsIDragService* mDragService;
 
   NSOpenGLContext *mGLContext;
@@ -271,17 +275,16 @@ typedef NSInteger NSEventGestureAxis;
 
 - (void)sendMouseEnterOrExitEvent:(NSEvent*)aEvent
                             enter:(BOOL)aEnter
                          exitFrom:(mozilla::WidgetMouseEvent::ExitFrom)aExitFrom;
 
 - (void)updateGLContext;
 - (void)_surfaceNeedsUpdate:(NSNotification*)notification;
 
-- (void)setGLContext:(NSOpenGLContext *)aGLContext;
 - (bool)preRender:(NSOpenGLContext *)aGLContext;
 - (void)postRender:(NSOpenGLContext *)aGLContext;
 
 - (BOOL)isCoveringTitlebar;
 
 - (void)viewWillStartLiveResize;
 - (void)viewDidEndLiveResize;
 

--- a/widget/cocoa/nsChildView.mm
+++ b/widget/cocoa/nsChildView.mm
@@ -3361,16 +3361,18 @@ NSEvent* gLastDragMouseDownEvent = nil;
     mCumulativeRotation = 0.0;
 
     // We can't call forceRefreshOpenGL here because, in order to work around
     // the bug, it seems we need to have a draw already happening. Therefore,
     // we call it in drawRect:inContext:, when we know that a draw is in
     // progress.
     mDidForceRefreshOpenGL = NO;
 
+    mNeedsGLUpdate = NO;
+
     [self setFocusRingType:NSFocusRingTypeNone];
 
 #ifdef __LP64__
     mCancelSwipeAnimation = nil;
 #endif
 
     mTopLeftCornerMask = NULL;
   }
@@ -3452,27 +3454,19 @@ NSEvent* gLastDragMouseDownEvent = nil;
 // again.
 // This can cause a flash in new windows - bug 631339 - but it's very hard to
 // fix that while maintaining this workaround.
 - (void)forceRefreshOpenGL
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
 
   [mGLContext clearDrawable];
+  CGLLockContext((CGLContextObj)[mGLContext CGLContextObj]);
   [self updateGLContext];
-
-  NS_OBJC_END_TRY_ABORT_BLOCK;
-}
-
-- (void)setGLContext:(NSOpenGLContext *)aGLContext
-{
-  NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
-
-  mGLContext = aGLContext;
-  [mGLContext retain];
+  CGLUnlockContext((CGLContextObj)[mGLContext CGLContextObj]);
 
   NS_OBJC_END_TRY_ABORT_BLOCK;
 }
 
 - (bool)preRender:(NSOpenGLContext *)aGLContext
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK_RETURN;
 
@@ -3480,22 +3474,28 @@ NSEvent* gLastDragMouseDownEvent = nil;
       ([[self window] isKindOfClass:[BaseWindow class]] &&
        ![(BaseWindow*)[self window] isVisibleOrBeingShown])) {
     // Before the window is shown, our GL context's front FBO is not
     // framebuffer complete, so we refuse to render.
     return false;
   }
 
   if (!mGLContext) {
-    [self setGLContext:aGLContext];
-    [self updateGLContext];
+    mGLContext = aGLContext;
+    [mGLContext retain];
+    mNeedsGLUpdate = true;
   }
 
   CGLLockContext((CGLContextObj)[aGLContext CGLContextObj]);
 
+  if (mNeedsGLUpdate) {
+    [self updateGLContext];
+    mNeedsGLUpdate = NO;
+  }
+
   return true;
 
   NS_OBJC_END_TRY_ABORT_BLOCK_RETURN(false);
 }
 
 - (void)postRender:(NSOpenGLContext *)aGLContext
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
@@ -3717,27 +3717,27 @@ NSEvent* gLastDragMouseDownEvent = nil;
 {
   // Return YES so that _regionForOpaqueDescendants gets called, where the
   // actual draggable region will be assembled.
   return YES;
 }
 
 -(void)updateGLContext
 {
-  if (mGLContext) {
-    CGLLockContext((CGLContextObj)[mGLContext CGLContextObj]);
-    [mGLContext setView:self];
-    [mGLContext update];
-    CGLUnlockContext((CGLContextObj)[mGLContext CGLContextObj]);
-  }
+  [mGLContext setView:self];
+  [mGLContext update];
 }
 
 - (void)_surfaceNeedsUpdate:(NSNotification*)notification
 {
-   [self updateGLContext];
+  if (mGLContext) {
+    CGLLockContext((CGLContextObj)[mGLContext CGLContextObj]);
+    mNeedsGLUpdate = YES;
+    CGLUnlockContext((CGLContextObj)[mGLContext CGLContextObj]);
+  }
 }
 
 - (BOOL)wantsBestResolutionOpenGLSurface
 {
   return nsCocoaUtils::HiDPIEnabled() ? YES : NO;
 }
 
 - (void)viewDidChangeBackingProperties