Temporary workaround for flashing buts on Mac

content/browser/renderer_host/render_widget_host_view_mac.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/render_widget_host_view_mac.h"
 
 #import <objc/runtime.h>
 #include <OpenGL/gl.h>
 #include <QuartzCore/QuartzCore.h>
 
@@ skipping 586 matching lines @@
 ///////////////////////////////////////////////////////////////////////////////
 // RenderWidgetHostViewMac, RenderWidgetHostView implementation:
 
 void RenderWidgetHostViewMac::EnsureBrowserCompositorView() {
   TRACE_EVENT0("browser",
                "RenderWidgetHostViewMac::EnsureBrowserCompositorView");
 
   // Create the view, to transition from Destroyed -> Suspended.
   if (browser_compositor_state_ == BrowserCompositorDestroyed) {
     browser_compositor_ = BrowserCompositorMac::Create();
+    browser_compositor_->compositor()->SetRootLayer(root_layer_.get());
     browser_compositor_->accelerated_widget_mac()->SetNSView(this);
     browser_compositor_state_ = BrowserCompositorSuspended;
   }
 
   // Show the DelegatedFrameHost to transition from Suspended -> Active.
   if (browser_compositor_state_ == BrowserCompositorSuspended) {
     delegated_frame_host_->SetCompositor(browser_compositor_->compositor());
     delegated_frame_host_->WasShown(ui::LatencyInfo());
-    browser_compositor_->compositor()->SetRootLayer(
-        root_layer_.get());
     browser_compositor_state_ = BrowserCompositorActive;
   }
 }
 
 void RenderWidgetHostViewMac::SuspendBrowserCompositorView() {
   TRACE_EVENT0("browser",
                "RenderWidgetHostViewMac::SuspendBrowserCompositorView");
 
   // Hide the DelegatedFrameHost to transition from Active -> Suspended.
   if (browser_compositor_state_ == BrowserCompositorActive) {
-    // Disconnect the root layer, which will prevent the compositor from
-    // producing more frames.
-    browser_compositor_->compositor()->SetRootLayer(nullptr);
     // Marking the DelegatedFrameHost as removed from the window hierarchy is
     // necessary to remove all connections to its old ui::Compositor.
     delegated_frame_host_->WasHidden();
     delegated_frame_host_->ResetCompositor();
     browser_compositor_state_ = BrowserCompositorSuspended;
   }
 }
 
 void RenderWidgetHostViewMac::DestroyBrowserCompositorView() {
   TRACE_EVENT0("browser",
                "RenderWidgetHostViewMac::DestroyBrowserCompositorView");
 
   // Transition from Active -> Suspended if need be.
   SuspendBrowserCompositorView();
 
   // Destroy the BrowserCompositorView to transition Suspended -> Destroyed.
   if (browser_compositor_state_ == BrowserCompositorSuspended) {
     browser_compositor_->accelerated_widget_mac()->ResetNSView();
     browser_compositor_->compositor()->SetScaleAndSize(1.0, gfx::Size(0, 0));
+    browser_compositor_->compositor()->SetRootLayer(nullptr);
     BrowserCompositorMac::Recycle(browser_compositor_.Pass());
     browser_compositor_state_ = BrowserCompositorDestroyed;
   }
 }
 
 void RenderWidgetHostViewMac::DestroySuspendedBrowserCompositorViewIfNeeded() {
   if (browser_compositor_state_ != BrowserCompositorSuspended)
     return;
 
   // If this view is in a window that is visible, keep around the suspended
@@ skipping 2724 matching lines @@
 
 // "-webkit-app-region: drag | no-drag" is implemented on Mac by excluding
 // regions that are not draggable. (See ControlRegionView in
 // native_app_window_cocoa.mm). This requires the render host view to be
 // draggable by default.
 - (BOOL)mouseDownCanMoveWindow {
   return YES;
 }
 
 @end