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

content/renderer/pepper/pepper_plugin_instance_impl.cc

Index: content/renderer/pepper/pepper_plugin_instance_impl.cc
diff --git a/content/renderer/pepper/pepper_plugin_instance_impl.cc b/content/renderer/pepper/pepper_plugin_instance_impl.cc
index 768922ec459976eb4f1750f30bbfdd1f66fbd7c0..8d97178015df84f49a27fadc4c147436ffd8c218 100644
--- a/content/renderer/pepper/pepper_plugin_instance_impl.cc
+++ b/content/renderer/pepper/pepper_plugin_instance_impl.cc
@@ -1957,6 +1957,8 @@ bool PepperPluginInstanceImpl::PrintPDFOutput(PP_Resource print_output,
 void PepperPluginInstanceImpl::UpdateLayer(bool device_changed) {
   if (!container_)
     return;
+  if (throttler_ && throttler_->IsHiddenForPlaceholder())
+    return;
 
   gpu::Mailbox mailbox;
   uint32 sync_point = 0;
@@ -2043,6 +2045,14 @@ void PepperPluginInstanceImpl::OnThrottleStateChange() {
   SendDidChangeView();
 }
 
+void PepperPluginInstanceImpl::OnHiddenForPlaceholder(bool hidden) {
+  if (hidden) {
+    container_->setWebLayer(nullptr);
+  } else {
+    UpdateLayer(true /* device_changed */);
+  }
+}
+
 void PepperPluginInstanceImpl::AddLatencyInfo(
     const std::vector<ui::LatencyInfo>& latency_info) {
   if (render_frame_ && render_frame_->GetRenderWidget()) {