Plugin Power Saver: Add UI Overlay to throttled plugin using placeholder.

content/renderer/pepper/pepper_plugin_instance_impl.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/renderer/pepper/pepper_plugin_instance_impl.h"
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/logging.h"
 #include "base/memory/linked_ptr.h"
@@ skipping 2025 matching lines @@
   return bound_graphics_2d_platform_->PrepareTextureMailbox(mailbox,
                                                             release_callback);
 }
 
 void PepperPluginInstanceImpl::OnDestruct() { render_frame_ = NULL; }
 
 void PepperPluginInstanceImpl::OnThrottleStateChange() {
   SendDidChangeView();
 }
 
+void PepperPluginInstanceImpl::OnHiddenForPlaceholder(bool hidden) {
+  if (hidden) {

[piman, 2015/02/05 00:34:36]

thinking about this a little more, you also need to keep this as a state, and
prevent UpdateLayer when it's set.
Otherwise what could happen is that the plugin is set as hidden because of the
placeholder, but then it decides for any reason to bind a new Graphics2D (or
3D), which will then call UpdateLayer and reattach to the tree.
I think you just need to keep a hidden_for_placeholder_ flag, and early exit in
UpdateLayer if it's set.

[tommycli, 2015/02/05 00:46:35]

Done. I put this flag in the throttler, since dmichael told me to try to
minimize additions to PepperPluginInstanceImpl. Let me know if this is fine.

+    container_->setWebLayer(nullptr);
+  } else {
+    UpdateLayer(true /* device_changed */);
+  }
+}
+
 void PepperPluginInstanceImpl::AddLatencyInfo(
     const std::vector<ui::LatencyInfo>& latency_info) {
   if (render_frame_ && render_frame_->GetRenderWidget()) {
     RenderWidgetCompositor* compositor =
         render_frame_->GetRenderWidget()->compositor();
     if (compositor) {
       for (size_t i = 0; i < latency_info.size(); i++) {
         scoped_ptr<cc::SwapPromise> swap_promise(
             new cc::LatencyInfoSwapPromise(latency_info[i]));
         compositor->QueueSwapPromise(swap_promise.Pass());
@@ skipping 1221 matching lines @@
 
 void PepperPluginInstanceImpl::RecordFlashJavaScriptUse() {
   if (!javascript_used_ && is_flash_plugin_) {
     javascript_used_ = true;
     RenderThread::Get()->RecordAction(
         base::UserMetricsAction("Flash.JavaScriptUsed"));
   }
 }
 
 }  // namespace content