Set cc::Display visibility to false when going to the background.

content/browser/renderer_host/compositor_impl_android.cc

 // 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/compositor_impl_android.h"
 
 #include <android/bitmap.h>
 #include <android/native_window_jni.h>
 #include <stdint.h>
 #include <unordered_set>
@@ skipping 541 matching lines @@
   TRACE_EVENT1("cc", "CompositorImpl::SetVisible", "visible", visible);
   if (!visible) {
     DCHECK(host_->IsVisible());
 
     // Make a best effort to try to complete pending readbacks.
     // TODO(crbug.com/637035): Consider doing this in a better way,
     // ideally with the guarantee of readbacks completing.
     if (display_.get() && HavePendingReadbacks())
       display_->ForceImmediateDrawAndSwapIfPossible();
 
+    if (display_)
+      display_->SetVisible(false);
     host_->SetVisible(false);
     host_->ReleaseCompositorFrameSink();
     has_compositor_frame_sink_ = false;
     pending_frames_ = 0;
     display_.reset();

[boliu, 2017/06/02 00:30:35]

we reset the display a few lines below, does this code really matter?

   } else {
+    if (display_)
+      display_->SetVisible(true);
     host_->SetVisible(true);
     if (compositor_frame_sink_request_pending_)
       HandlePendingCompositorFrameSinkRequest();
   }
 }
 
 void CompositorImpl::SetWindowBounds(const gfx::Size& size) {
   if (size_ == size)
     return;
 
@@ skipping 210 matching lines @@
   auto compositor_frame_sink =
       vulkan_context_provider
           ? base::MakeUnique<cc::DirectCompositorFrameSink>(
                 frame_sink_id_, manager, display_.get(),
                 vulkan_context_provider)
           : base::MakeUnique<cc::DirectCompositorFrameSink>(
                 frame_sink_id_, manager, display_.get(), context_provider,
                 nullptr, BrowserGpuMemoryBufferManager::current(),
                 viz::HostSharedBitmapManager::current());
 
-  display_->SetVisible(true);
+  display_->SetVisible(host_->IsVisible());
   display_->Resize(size_);
   host_->SetCompositorFrameSink(std::move(compositor_frame_sink));
 }
 
 void CompositorImpl::DidSwapBuffers() {
   client_->DidSwapBuffers();
 }
 
 cc::UIResourceId CompositorImpl::CreateUIResource(
     cc::UIResourceClient* client) {
@@ skipping 72 matching lines @@
   }
   GetSurfaceManager()->UnregisterFrameSinkHierarchy(frame_sink_id_,
                                                     frame_sink_id);
 }
 
 bool CompositorImpl::HavePendingReadbacks() {
   return !readback_layer_tree_->children().empty();
 }
 
 }  // namespace content