Use GetInverse

ash/ash_root_window_transformer.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/ash_root_window_transformer.h"
 
 #include "ui/aura/root_window.h"
 #include "ui/compositor/dip_util.h"
 #include "ui/gfx/size_conversions.h"
 
 namespace ash {
 
 AshRootWindowTransformer::AshRootWindowTransformer(
     aura::RootWindow* root,
     const gfx::Transform& transform,
-    const gfx::Transform& inverted,
     const gfx::Insets& host_insets,
     float root_window_scale)
     : root_window_(root),
       transform_(transform),
       root_window_scale_(root_window_scale),
       host_insets_(host_insets) {
   root_window_->layer()->SetForceRenderSurface(root_window_scale_ != 1.0f);
 
   gfx::Transform translate;
-  invert_transform_ = inverted;
-  invert_transform_.Scale(root_window_scale_, root_window_scale_);
 
   if (host_insets.top() != 0 || host_insets.left() != 0) {
     float device_scale_factor = ui::GetDeviceScaleFactor(root_window_->layer());
     float x_offset = host_insets.left() / device_scale_factor;
     float y_offset = host_insets.top() / device_scale_factor;
     translate.Translate(x_offset, y_offset);
-    invert_transform_.Translate(-x_offset, -y_offset);
   }
   float inverted_scale = 1.0f / root_window_scale_;
   translate.Scale(inverted_scale, inverted_scale);
+  transform_ = translate * transform;
 
-  transform_ = translate * transform;
+  CHECK(transform_.GetInverse(&invert_transform_));
 }
 
 gfx::Transform AshRootWindowTransformer::GetTransform() const {
   return transform_;
 }
 
 gfx::Transform AshRootWindowTransformer::GetInverseTransform() const {
   return invert_transform_;
 }
 
@@ skipping 19 matching lines @@
   // backing pixel when |root_window_scale_| is specified
   // (850 height at 1.25 scale becomes 1062.5 for example.)
   return gfx::Rect(gfx::ToFlooredSize(new_bounds.size()));
 }
 
 gfx::Insets AshRootWindowTransformer::GetHostInsets() const {
   return host_insets_;
 }
 
 }  // namespace ash