Enforce constant size and device scale factor for surfaces

ui/aura/local/compositor_frame_sink_local.cc

 // Copyright 2017 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 "ui/aura/local/compositor_frame_sink_local.h"
 
 #include "cc/output/compositor_frame_sink_client.h"
 #include "cc/surfaces/compositor_frame_sink_support.h"
 #include "ui/aura/client/cursor_client.h"
 #include "ui/aura/env.h"
@@ skipping 45 matching lines @@
   thread_checker_.reset();
   cc::CompositorFrameSink::DetachFromClient();
 }
 
 void CompositorFrameSinkLocal::SubmitCompositorFrame(
     cc::CompositorFrame frame) {
   DCHECK(thread_checker_);
   DCHECK(thread_checker_->CalledOnValidThread());
 
   cc::LocalSurfaceId old_local_surface_id = local_surface_id_;
-  if (!frame.render_pass_list.empty()) {
-    const auto& frame_size = frame.render_pass_list.back()->output_rect.size();
-    if (frame_size != last_submitted_frame_size_ ||
-        !local_surface_id_.is_valid()) {
-      last_submitted_frame_size_ = frame_size;
-      local_surface_id_ = id_allocator_.GenerateId();
-    }
+  const auto& frame_size = frame.render_pass_list.back()->output_rect.size();
+  if (frame_size != surface_size_ ||
+      frame.metadata.device_scale_factor != device_scale_factor_ ||
+      !local_surface_id_.is_valid()) {
+    surface_size_ = frame_size;
+    device_scale_factor_ = frame.metadata.device_scale_factor;
+    local_surface_id_ = id_allocator_.GenerateId();
   }
-  support_->SubmitCompositorFrame(local_surface_id_, std::move(frame));
+  bool result =
+      support_->SubmitCompositorFrame(local_surface_id_, std::move(frame));
+  DCHECK(result);
 
   if (local_surface_id_ != old_local_surface_id) {
     surface_changed_callback_.Run(
-        cc::SurfaceId(frame_sink_id_, local_surface_id_),
-        last_submitted_frame_size_);
+        cc::SurfaceId(frame_sink_id_, local_surface_id_), surface_size_);
   }
 }
 
 void CompositorFrameSinkLocal::DidReceiveCompositorFrameAck(
     const cc::ReturnedResourceArray& resources) {
   DCHECK(thread_checker_);
   DCHECK(thread_checker_->CalledOnValidThread());
   if (!client_)
     return;
   if (!resources.empty())
@@ skipping 24 matching lines @@
 
 void CompositorFrameSinkLocal::OnDidFinishFrame(const cc::BeginFrameAck& ack) {
   DCHECK(thread_checker_);
   DCHECK(thread_checker_->CalledOnValidThread());
   // If there was damage, the submitted CompositorFrame includes the ack.
   if (!ack.has_damage)
     support_->BeginFrameDidNotSwap(ack);
 }
 
 }  // namespace aura