Enqueuing new frames in a Surface should cause Displays to reaggregate it

content/browser/compositor/delegated_frame_host.cc

 // Copyright 2014 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/compositor/delegated_frame_host.h"
 
 #include "base/callback_helpers.h"
 #include "base/command_line.h"
 #include "cc/output/compositor_frame.h"
 #include "cc/output/compositor_frame_ack.h"
@@ skipping 332 matching lines @@
     if (resource_collection_.get()) {
       resource_collection_->SetClient(NULL);
 
       if (resource_collection_->LoseAllResources())
         SendReturnedDelegatedResources(last_output_surface_id_);
 
       resource_collection_ = NULL;
     }
     last_output_surface_id_ = output_surface_id;
   }
+  bool modified_layers = false;
   if (frame_size.IsEmpty()) {
     DCHECK(frame_data->resource_list.empty());
     EvictDelegatedFrame();
+    modified_layers = true;
   } else {
     if (use_surfaces_) {
       if (!surface_factory_) {
         ImageTransportFactory* factory = ImageTransportFactory::GetInstance();
         cc::SurfaceManager* manager = factory->GetSurfaceManager();
         id_allocator_ = factory->CreateSurfaceIdAllocator();
         surface_factory_ =
             make_scoped_ptr(new cc::SurfaceFactory(manager, this));
       }
       if (surface_id_.is_null() || frame_size != current_surface_size_ ||
           frame_size_in_dip != current_frame_size_in_dip_) {
+        // TODO(jbauman): Wait to destroy this surface until the parent has
+        // finished using it.
         if (!surface_id_.is_null())
           surface_factory_->Destroy(surface_id_);
         surface_id_ = id_allocator_->GenerateId();
         surface_factory_->Create(surface_id_, frame_size);
         client_->GetLayer()->SetShowSurface(surface_id_, frame_size_in_dip);
         current_surface_size_ = frame_size;
+        modified_layers = true;
       }
       scoped_ptr<cc::CompositorFrame> compositor_frame =
           make_scoped_ptr(new cc::CompositorFrame());
       compositor_frame->delegated_frame_data = frame_data.Pass();
       surface_factory_->SubmitFrame(surface_id_, compositor_frame.Pass());
     } else {
       if (!resource_collection_) {
         resource_collection_ = new cc::DelegatedFrameResourceCollection;
         resource_collection_->SetClient(this);
       }
       // If the physical frame size changes, we need a new |frame_provider_|. If
       // the physical frame size is the same, but the size in DIP changed, we
       // need to adjust the scale at which the frames will be drawn, and we do
       // this by making a new |frame_provider_| also to ensure the scale change
       // is presented in sync with the new frame content.
       if (!frame_provider_.get() ||
           frame_size != frame_provider_->frame_size() ||
           frame_size_in_dip != current_frame_size_in_dip_) {
         frame_provider_ = new cc::DelegatedFrameProvider(
             resource_collection_.get(), frame_data.Pass());
         client_->GetLayer()->SetShowDelegatedContent(frame_provider_.get(),
                                                      frame_size_in_dip);
       } else {
         frame_provider_->SetFrameData(frame_data.Pass());
       }
+      modified_layers = true;
     }
   }
   released_front_lock_ = NULL;
   current_frame_size_in_dip_ = frame_size_in_dip;
   CheckResizeLock();
 
-  client_->SchedulePaintInRect(damage_rect_in_dip);
+  if (modified_layers) {
+    // TODO(jbauman): Need to always tell the window observer about the
+    // damage.
+    client_->SchedulePaintInRect(damage_rect_in_dip);
+  }
 
   pending_delegated_ack_count_++;
 
   ui::Compositor* compositor = client_->GetCompositor();
-  if (!compositor) {
+  if (!compositor || !modified_layers) {
     SendDelegatedFrameAck(output_surface_id);
   } else {
     std::vector<ui::LatencyInfo>::const_iterator it;
     for (it = latency_info.begin(); it != latency_info.end(); ++it)
       compositor->SetLatencyInfo(*it);
     // If we've previously skipped any latency infos add them.
     for (it = skipped_latency_info_list_.begin();
         it != skipped_latency_info_list_.end();
         ++it)
       compositor->SetLatencyInfo(*it);
@@ skipping 496 matching lines @@
   if (frame_provider_.get()) {
     new_layer->SetShowDelegatedContent(frame_provider_.get(),
                                        current_frame_size_in_dip_);
   }
   if (!surface_id_.is_null()) {
     new_layer->SetShowSurface(surface_id_, current_frame_size_in_dip_);
   }
 }
 
 }  // namespace content