[content] Fix background color update handling in RWHVAura.

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 <Carbon/Carbon.h>
 #import <objc/runtime.h>
 #include <OpenGL/gl.h>
 #include <QuartzCore/QuartzCore.h>
@@ skipping 431 matching lines @@
 
 RenderWidgetHostViewMac::RenderWidgetHostViewMac(RenderWidgetHost* widget,
                                                  bool is_guest_view_hack)
     : render_widget_host_(RenderWidgetHostImpl::From(widget)),
       page_at_minimum_scale_(true),
       is_loading_(false),
       allow_pause_for_resize_or_repaint_(true),
       is_guest_view_hack_(is_guest_view_hack),
       fullscreen_parent_host_view_(nullptr),
       needs_flush_input_(false),
+      background_color_(SK_ColorWHITE),
       weak_factory_(this) {
   // |cocoa_view_| owns us and we will be deleted when |cocoa_view_|
   // goes away.  Since we autorelease it, our caller must put
   // |GetNativeView()| into the view hierarchy right after calling us.
   cocoa_view_ = [[[RenderWidgetHostViewCocoa alloc]
                   initWithRenderWidgetHostViewMac:this] autorelease];
 
   // Paint this view host with |background_color_| when there is no content
   // ready to draw.
   background_layer_.reset([[CALayer alloc] init]);
@@ skipping 965 matching lines @@
   browser_compositor_->DidCreateNewRendererCompositorFrameSink();
 }
 
 void RenderWidgetHostViewMac::SubmitCompositorFrame(
     const cc::LocalSurfaceId& local_surface_id,
     cc::CompositorFrame frame) {
   TRACE_EVENT0("browser", "RenderWidgetHostViewMac::OnSwapCompositorFrame");
 
   // Override the compositor background color. See RenderWidgetHostViewAura
   // for more details.
   SetBackgroundColor(frame.metadata.root_background_color);

[lfg, 2017/04/06 18:37:59]

Let's apply the same fix here as you have done for Aura.

[Eric Seckler, 2017/04/07 08:27:41]

Ah, didn't realize this was added to RWHVMac now, too. Done.

 
   last_scroll_offset_ = frame.metadata.root_scroll_offset;
 
   page_at_minimum_scale_ =
       frame.metadata.page_scale_factor == frame.metadata.min_page_scale_factor;
   browser_compositor_->SubmitCompositorFrame(local_surface_id,
                                              std::move(frame));
   UpdateDisplayVSyncParameters();
 }
 
@@ skipping 189 matching lines @@
 }
 
 void RenderWidgetHostViewMac::ShowDefinitionForSelection() {
   RenderWidgetHostViewMacDictionaryHelper helper(this);
   helper.ShowDefinitionForSelection();
 }
 
 void RenderWidgetHostViewMac::SetBackgroundColor(SkColor color) {
   if (color == background_color_)
     return;
+  background_color_ = color;
 
-  RenderWidgetHostViewBase::SetBackgroundColor(color);
-  bool opaque = GetBackgroundOpaque();
+  DCHECK(SkColorGetA(color) == SK_AlphaOPAQUE ||
+         SkColorGetA(color) == SK_AlphaTRANSPARENT);
+  bool opaque = SkColorGetA(color) == SK_AlphaOPAQUE;
 
   if (render_widget_host_)
     render_widget_host_->SetBackgroundOpaque(opaque);
 
   [cocoa_view_ setOpaque:opaque];
 
   browser_compositor_->SetHasTransparentBackground(!opaque);
 
   ScopedCAActionDisabler disabler;
   base::ScopedCFTypeRef<CGColorRef> cg_color(
       skia::CGColorCreateFromSkColor(color));
   [background_layer_ setBackgroundColor:cg_color];
 }
 
+SkColor RenderWidgetHostViewMac::background_color() const {
+  return background_color_;
+}
+
 BrowserAccessibilityManager*
     RenderWidgetHostViewMac::CreateBrowserAccessibilityManager(
         BrowserAccessibilityDelegate* delegate, bool for_root_frame) {
   return new BrowserAccessibilityManagerMac(
       BrowserAccessibilityManagerMac::GetEmptyDocument(), delegate);
 }
 
 gfx::Point RenderWidgetHostViewMac::AccessibilityOriginInScreen(
     const gfx::Rect& bounds) {
   NSPoint origin = NSMakePoint(bounds.x(), bounds.y());
@@ skipping 1833 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