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..2a52c710f5a975cbd70f8e375ac441a4d8b62827 100644
--- a/content/renderer/pepper/pepper_plugin_instance_impl.cc
+++ b/content/renderer/pepper/pepper_plugin_instance_impl.cc
@@ -2043,6 +2043,14 @@ void PepperPluginInstanceImpl::OnThrottleStateChange() {
   SendDidChangeView();
 }
 
+void PepperPluginInstanceImpl::UpdateVisibility(bool visible) {
+  if (visible) {
+    UpdateLayer(true /* device_changed */);
+  } else {
+    container_->setWebLayer(nullptr);

[piman, 2015/02/04 01:14:38]

When is this called exactly? Why are we doing this?
Taking the layer out of the tree has consequences such as the layer not
committing any more, which has implications wrt graphics callbacks.

[tommycli, 2015/02/04 01:18:04]

Hey,

This is called when we want to keep the plugin alive, but not draw it anymore.
The call path is:

LoadablePluginPlaceholder -> blink::WebPlugin::updateVisibility ->
PepperPluginInstanceImpl::UpdateVisibility.

We want to draw the placeholder instead. When I didn't do this, the 'real'
plugin kept drawing on top.

+  }
+}
+
 void PepperPluginInstanceImpl::AddLatencyInfo(
     const std::vector<ui::LatencyInfo>& latency_info) {
   if (render_frame_ && render_frame_->GetRenderWidget()) {