MacViews: Implement BridgedNativeWidget::OnDeviceScaleFactorChanged function.

ui/views/cocoa/bridged_native_widget.mm

 // 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.
 
 #import "ui/views/cocoa/bridged_native_widget.h"
 
 #import <objc/runtime.h>
 
 #include "base/logging.h"
 #import "base/mac/foundation_util.h"
@@ skipping 855 matching lines @@
   native_widget_mac_->GetWidget()->OnNativeWidgetPaint(context);
 }
 
 void BridgedNativeWidget::OnDelegatedFrameDamage(
     const gfx::Rect& damage_rect_in_dip) {
   NOTIMPLEMENTED();
 }
 
 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() {
   NOTIMPLEMENTED();
   return base::Closure();
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // BridgedNativeWidget, AcceleratedWidgetMac:
 
@@ skipping 283 matching lines @@
   [bridged_view_ setMouseDownCanMoveWindow:draggable];
   // AppKit will not update its cache of mouseDownCanMoveWindow unless something
   // changes. Previously we tried adding an NSView and removing it, but for some
   // reason it required reposting the mouse-down event, and didn't always work.
   // Calling the below seems to be an effective solution.
   [window_ setMovableByWindowBackground:NO];
   [window_ setMovableByWindowBackground:YES];
 }
 
 }  // namespace views