Enforce constant size and device scale factor for surfaces

cc/test/test_compositor_frame_sink.cc

Index: cc/test/test_compositor_frame_sink.cc
diff --git a/cc/test/test_compositor_frame_sink.cc b/cc/test/test_compositor_frame_sink.cc
index dd0fd2adee3ab5d247af9abba7713555cb93bcb2..ea7856e5fe481f2b8a4128ccfe6d45b2b3d83cac 100644
--- a/cc/test/test_compositor_frame_sink.cc
+++ b/cc/test/test_compositor_frame_sink.cc
@@ -128,17 +128,18 @@ void TestCompositorFrameSink::SetLocalSurfaceId(
 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();
-  }
-  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);
+  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;
+  }
 
-  support_->SubmitCompositorFrame(delegated_local_surface_id_,
-                                  std::move(frame));
+  support_->SubmitCompositorFrame(local_surface_id_, std::move(frame));
 
   for (std::unique_ptr<CopyOutputRequest>& copy_request : copy_requests_) {
     support_->RequestCopyOfSurface(std::move(copy_request));