Seems incorrect to se device_scale_factor in SetLocalSurfaceId.

cc/surfaces/display.cc

Index: cc/surfaces/display.cc
diff --git a/cc/surfaces/display.cc b/cc/surfaces/display.cc
index 2a83572c9f51d24f370648f2edf22be5a87d7eef..db80bcb167825a6bc1c870619957a14549807d6a 100644
--- a/cc/surfaces/display.cc
+++ b/cc/surfaces/display.cc
@@ -104,22 +104,28 @@ void Display::Initialize(DisplayClient* client,
   }
 }
 
-void Display::SetLocalSurfaceId(const LocalSurfaceId& id,
-                                float device_scale_factor) {
-  if (current_surface_id_.local_surface_id() == id &&
-      device_scale_factor_ == device_scale_factor) {
+void Display::SetLocalSurfaceId(const LocalSurfaceId& id) {
+  if (current_surface_id_.local_surface_id() == id) {

[Fady Samuel, 2017/02/02 16:34:29]

drop the braces { and }.

     return;
   }
 
   TRACE_EVENT0("cc", "Display::SetSurfaceId");
   current_surface_id_ = SurfaceId(frame_sink_id_, id);
-  device_scale_factor_ = device_scale_factor;
 
   UpdateRootSurfaceResourcesLocked();
   if (scheduler_)
     scheduler_->SetNewRootSurface(current_surface_id_);
 }
 
+void Display::SetDeviceScaleFactor(float device_scale_factor) {
+  if (device_scale_factor_ == device_scale_factor) {
+    return;
+  }
+
+  TRACE_EVENT0("cc", "Display::SetDeviceScaleFactor");
+  device_scale_factor_ = device_scale_factor;

[Fady Samuel, 2017/02/02 16:34:29]

We might want to mark SurfaceDamaged here. 

[k.devara, 2017/02/03 11:35:37]

I was thinking device_scale_factor may not trigger a damage.\, unlike Resize?
you should be able to set the device_scale_factor for display, without damaging
the surface?

+}
+
 void Display::SetVisible(bool visible) {
   TRACE_EVENT1("cc", "Display::SetVisible", "visible", visible);
   if (renderer_)