MacViews: Implement BridgedNativeWidget::OnDeviceScaleFactorChanged function.

ui/views/cocoa/bridged_native_widget.mm

Index: ui/views/cocoa/bridged_native_widget.mm
diff --git a/ui/views/cocoa/bridged_native_widget.mm b/ui/views/cocoa/bridged_native_widget.mm
index b91f5b4b2d330a305cbb8ef482eebbe8efa5134e..1def3dcaa427caa371f9494f70d735e774817074 100644
--- a/ui/views/cocoa/bridged_native_widget.mm
+++ b/ui/views/cocoa/bridged_native_widget.mm
@@ -873,7 +873,8 @@ void BridgedNativeWidget::OnDelegatedFrameDamage(
 
 void BridgedNativeWidget::OnDeviceScaleFactorChanged(
     float device_scale_factor) {
-  NOTIMPLEMENTED();
+  native_widget_mac_->GetWidget()->DeviceScaleFactorChanged(

[tapted, 2015/12/17 22:38:20]

E.g. here a good test would be in widget_unittest.cc, something like

class ScaleFactorView : public View {
..
  // Overridden from ui::LayerDelegate:
  void OnDeviceScaleFactorChanged(float device_scale_factor) override {
    last_scale_factor_ = device_scale_factor;
    View::OnDeviceScaleFactorChanged(device_scale_factor);
  }
  float last_scale_factor() const { return last_scale_factor_; };
..
 private:
  float last_scale_factor_ = 0;

  DISALLOW..etc
};

TEST_F(WidgetTest, OnDeviceScaleFactorChanged) {
  Widget* widget = CreateTopLevelPlatformWidget();
  ScaleFactorView* view = new ScaleFactorView;  
  widget->GetContentsView->AddChildView(view);
  
  // Adding the view should notify the view about the initial scale factor.
  EXPECT_EQ(1.0f, view->last_scale_factor());

  // Changes should be propagated.
  widget->GetLayer()->OnDeviceScaleFactorChanged(2.0f);
  EXPECT_EQ(2.0f, view->last_scale_factor());
  
  widget->CloseNow();
}

[Andrey Kraynov, 2015/12/18 13:51:59]

OK, I've tried to run this test.
But it seems that assumption that the parent view should notify the child view
about the initial scale factor
fails both on Win and Mac. First expect in this test always fails.

Could you point me to the code that leads to expected behavior?
Is it a bug that should be fixed?

+      device_scale_factor);
 }
 
 base::Closure BridgedNativeWidget::PrepareForLayerBoundsChange() {