Enforce constant size and device scale factor for surfaces

cc/test/test_compositor_frame_sink.cc

 // Copyright 2016 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 "cc/test/test_compositor_frame_sink.h"
 
 #include <stdint.h>
 #include <utility>
 
 #include "base/memory/ptr_util.h"
@@ skipping 111 matching lines @@
 }
 
 void TestCompositorFrameSink::SetLocalSurfaceId(
     const LocalSurfaceId& local_surface_id) {
   test_client_->DisplayReceivedLocalSurfaceId(local_surface_id);
 }
 
 void TestCompositorFrameSink::SubmitCompositorFrame(CompositorFrame frame) {
   test_client_->DisplayReceivedCompositorFrame(frame);
 
-  if (!delegated_local_surface_id_.is_valid()) {
-    delegated_local_surface_id_ = local_surface_id_allocator_->GenerateId();
+  gfx::Size frame_size = frame.render_pass_list.back()->output_rect.size();
+  float device_scale_factor = frame.metadata.device_scale_factor;
+  if (!local_surface_id_.is_valid() || frame_size != display_size_ ||
+      device_scale_factor != device_scale_factor_) {
+    local_surface_id_ = local_surface_id_allocator_->GenerateId();
+    display_->SetLocalSurfaceId(local_surface_id_, device_scale_factor);
+    display_->Resize(frame_size);
+    display_size_ = frame_size;
+    device_scale_factor_ = device_scale_factor;
   }
-  display_->SetLocalSurfaceId(delegated_local_surface_id_,
-                              frame.metadata.device_scale_factor);
 
-  gfx::Size frame_size = frame.render_pass_list.back()->output_rect.size();
-  display_->Resize(frame_size);
-
-  support_->SubmitCompositorFrame(delegated_local_surface_id_,
-                                  std::move(frame));
+  DCHECK(support_->SubmitCompositorFrame(local_surface_id_, std::move(frame)));

[danakj, 2017/05/19 19:00:59]

here's another

 
   for (std::unique_ptr<CopyOutputRequest>& copy_request : copy_requests_) {
     support_->RequestCopyOfSurface(std::move(copy_request));
   }
   copy_requests_.clear();
 
   if (!display_->has_scheduler()) {
     display_->DrawAndSwap();
     // Post this to get a new stack frame so that we exit this function before
     // calling the client to tell it that it is done.
@@ skipping 45 matching lines @@
   support_->SetNeedsBeginFrame(needs_begin_frames);
 }
 
 void TestCompositorFrameSink::OnDidFinishFrame(const BeginFrameAck& ack) {}
 
 void TestCompositorFrameSink::SendCompositorFrameAckToClient() {
   client_->DidReceiveCompositorFrameAck();
 }
 
 }  // namespace cc