Seems incorrect to se device_scale_factor in SetLocalSurfaceId.

cc/surfaces/display.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 "cc/surfaces/display.h"
 
 #include <stddef.h>
 
 #include "base/memory/ptr_util.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 86 matching lines @@
     // on the same callstack as the ContextProvider being created/initialized
     // or else it could miss a callback before setting this.
     context->SetLostContextCallback(base::Bind(
         &Display::DidLoseContextProvider,
         // Unretained is safe since the callback is unset in this class'
         // destructor and is never posted.
         base::Unretained(this)));
   }
 }
 
-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_)
     renderer_->SetVisible(visible);
   if (scheduler_)
     scheduler_->SetVisible(visible);
   visible_ = visible;
 
   if (!visible) {
     // Damage tracker needs a full reset as renderer resources are dropped when
@@ skipping 264 matching lines @@
 const SurfaceId& Display::CurrentSurfaceId() {
   return current_surface_id_;
 }
 
 void Display::ForceImmediateDrawAndSwapIfPossible() {
   if (scheduler_)
     scheduler_->ForceImmediateSwapIfPossible();
 }
 
 }  // namespace cc