aura: Allow delegated frames to be used by more than one impl layer.

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index 2f27455a8569096ecb3167f748ae9dedebffbcd1..63bbaa42a8fdc1fe0bb27a12509f1d3cb74f964c 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -12,6 +12,7 @@
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/string_number_conversions.h"
+#include "cc/layers/delegated_frame_provider.h"
 #include "cc/output/compositor_frame.h"
 #include "cc/output/compositor_frame_ack.h"
 #include "cc/output/copy_output_request.h"
@@ -1470,15 +1471,33 @@ void RenderWidgetHostViewAura::SwapDelegatedFrame(
     // resources from the old one with resources from the new one which would
     // have the same id. Changing the layer to showing painted content destroys
     // the DelegatedRendererLayer.
-    // TODO(danakj): Lose and return all resources in the delegated layer first.
     window_->layer()->SetShowPaintedContent();
+
+    // TODO(danakj): Lose all resources and send them back here, such as:
+    // resource_collection_->LoseAllResources();
+    // SendReturnedDelegatedResources(last_output_surface_id_);
+
+    // Drop the cc::DelegatedFrameResourceCollection so that we will not return
+    // any resources from the old output surface with the new output surface id.

[piman, 2013/10/04 23:42:25]

I wonder if we should have the DelegatedFrameResourceCollection manage the
output_surface_id somehow? When we receive the resources and create the DFRC, we
know exactly what surface id we're supposed to return them to. Then in
SendDelegatedFrameAck we could check the surface id the resource_collection_
corresponds to, and only return the resources through the SwapCompositorFrameAck
if it matches the surface id. If not, we can send the ReclaimCompositorResources
message (maybe? Or dropping resources is probably ok).

[danakj, 2013/10/07 21:57:39]

Hm, if I'm understanding your suggestion, we'll have replaced the
resource_collection_ just below here anyway. So we'd need to keep around the old
collection just to wait for the resources to come back, but the child won't want
them. That's why I think we should just force lose them here so we can tell the
child immediately and keep this simpler with only one resource collection alive.

[piman, 2013/10/08 03:38:08]

Ok. The thing I'm kinda worried is below in SendDelegatedFrameAck, I'm not sure
what guarantees the resources we take back come from the right
output_surface_id. But that's not specific to this patch, so we can iterate
later if it proves to be an issue.

+    frame_provider_.reset();
+    resource_collection_.reset();
     last_output_surface_id_ = output_surface_id;
   }
   if (frame_size.IsEmpty()) {
-    // TODO(danakj): Return all resources in the delegated layer somehow.
+    DCHECK_EQ(0u, frame_data->resource_list.size());
     window_->layer()->SetShowPaintedContent();
   } else {
-    window_->layer()->SetDelegatedFrame(frame_data.Pass(), frame_size_in_dip);
+    if (!resource_collection_)

[piman, 2013/10/04 23:42:25]

nit: needs {}

[danakj, 2013/10/07 21:57:39]

Done.

+      resource_collection_.reset(
+          new cc::DelegatedFrameResourceCollection(this));
+    if (!frame_provider_ || frame_size != frame_provider_->frame_size()) {
+      frame_provider_.reset(new cc::DelegatedFrameProvider(
+          resource_collection_.get(), frame_data.Pass()));
+      window_->layer()->SetShowDelegatedContent(frame_provider_.get(),
+                                                frame_size_in_dip);
+    } else {
+      frame_provider_->SetFrameData(frame_data.Pass());
+    }
   }
   released_front_lock_ = NULL;
   current_frame_size_ = frame_size_in_dip;
@@ -1503,10 +1522,16 @@ void RenderWidgetHostViewAura::SwapDelegatedFrame(
 
 void RenderWidgetHostViewAura::SendDelegatedFrameAck(uint32 output_surface_id) {
   cc::CompositorFrameAck ack;
-  window_->layer()->TakeUnusedResourcesForChildCompositor(&ack.resources);
-  RenderWidgetHostImpl::SendSwapCompositorFrameAck(
-      host_->GetRoutingID(), output_surface_id,
-      host_->GetProcess()->GetID(), ack);
+  if (resource_collection_)
+    resource_collection_->TakeUnusedResourcesForChildCompositor(&ack.resources);
+  RenderWidgetHostImpl::SendSwapCompositorFrameAck(host_->GetRoutingID(),
+                                                   output_surface_id,
+                                                   host_->GetProcess()->GetID(),
+                                                   ack);
+}
+
+void RenderWidgetHostViewAura::UnusedResourcesAreAvailable() {
+  // TODO(danakj): If no ack is pending, collect and send resources now.
 }
 
 void RenderWidgetHostViewAura::SwapSoftwareFrame(