Create RootWindowTransformer after root window's bounds and scale factor are updated.

ash/display/root_window_transformers.cc

 // Copyright (c) 2013 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 "ash/display/root_window_transformers.h"
 
 #include <cmath>
 
 #include "ash/display/display_info.h"
 #include "ash/display/display_manager.h"
@@ skipping 26 matching lines @@
   const float kEpsilon = 0.001f;
   SkMatrix44& matrix = transform->matrix();
   for (int x = 0; x < 4; ++x) {
     for (int y = 0; y < 4; ++y) {
       if (std::abs(SkMScalarToFloat(matrix.get(x, y))) < kEpsilon)
         matrix.set(x, y, SkFloatToMScalar(0.0f));
     }
   }
 }
 
+// TODO(oshima): Transformers should be able to adjust itself
+// when the device scale factor is changed, instead of
+// precalculating the transform using fixed value.
+
 gfx::Transform CreateRotationTransform(aura::RootWindow* root_window,
                                        const gfx::Display& display) {
   DisplayInfo info =
       Shell::GetInstance()->display_manager()->GetDisplayInfo(display.id());
 
   // TODO(oshima): Add animation. (crossfade+rotation, or just cross-fade)
 #if defined(OS_WIN)
   // Windows 8 bots refused to resize the host window, and
   // updating the transform results in incorrectly resizing
   // the root window. Don't apply the transform unless
@@ skipping 223 matching lines @@
 
 aura::RootWindowTransformer* CreateRootWindowTransformerForMirroredDisplay(
     const DisplayInfo& source_display_info,
     const DisplayInfo& mirror_display_info) {
   return new MirrorRootWindowTransformer(source_display_info,
                                          mirror_display_info);
 }
 
 }  // namespace internal
 }  // namespace ash