cc: Fix bug where tabs have the wrong scale factor

cc/trees/layer_tree_impl_unittest.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/trees/layer_tree_impl.h"
 
 #include "cc/layers/heads_up_display_layer_impl.h"
 #include "cc/layers/layer.h"
 #include "cc/layers/solid_color_scrollbar_layer_impl.h"
 #include "cc/test/fake_impl_task_runner_provider.h"
@@ skipping 2352 matching lines @@
 
 TEST_F(LayerTreeImplTest, NumLayersSmallTree) {
   EXPECT_EQ(0u, host_impl().active_tree()->NumLayers());
   scoped_ptr<LayerImpl> root = LayerImpl::Create(host_impl().active_tree(), 1);
   root->AddChild(LayerImpl::Create(host_impl().active_tree(), 2));
   root->AddChild(LayerImpl::Create(host_impl().active_tree(), 3));
   root->child_at(1)->AddChild(LayerImpl::Create(host_impl().active_tree(), 4));
   EXPECT_EQ(4u, host_impl().active_tree()->NumLayers());
 }
 
+TEST_F(LayerTreeImplTest, DeviceScaleFactorNeedsDrawPropertiesUpdate) {
+  host_impl().active_tree()->SetDeviceScaleFactor(1.f);
+  host_impl().active_tree()->UpdateDrawProperties(false);
+  EXPECT_FALSE(host_impl().active_tree()->needs_update_draw_properties());
+  host_impl().active_tree()->SetDeviceScaleFactor(2.f);
+  EXPECT_TRUE(host_impl().active_tree()->needs_update_draw_properties());
+}
+
 }  // namespace
 }  // namespace cc