MacViews: Implement BridgedNativeWidget::OnDeviceScaleFactorChanged function.

ui/views/widget/widget_unittest.cc

 // Copyright (c) 2012 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 <algorithm>
 #include <set>
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 3380 matching lines @@
 TEST_F(WidgetTest, AlwaysOnTop) {
   Widget* widget = CreateTopLevelNativeWidget();
   EXPECT_FALSE(widget->IsAlwaysOnTop());
   widget->SetAlwaysOnTop(true);
   EXPECT_TRUE(widget->IsAlwaysOnTop());
   widget->SetAlwaysOnTop(false);
   EXPECT_FALSE(widget->IsAlwaysOnTop());
   widget->CloseNow();
 }
 
+namespace {
+
+class ScaleFactorView : public View {
+ public:
+  ScaleFactorView() = default;

[sadrul, 2015/12/22 08:13:34]

How is this different from 'ScaleFactorView() {}'?

[Andrey Kraynov, 2015/12/22 08:38:57]

Both forms of ctor will behave the same here.
But '= default' syntax have some bonuses, there is nice post at
http://stackoverflow.com/questions/20828907/the-new-keyword-default-in-c11
And I prefer using it if possible.

+
+  // 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.f;
+
+  DISALLOW_COPY_AND_ASSIGN(ScaleFactorView);
+};
+
+struct WidgetCloser {
+  inline void operator()(Widget* widget) const { widget->CloseNow(); }
+};

[sadrul, 2015/12/22 08:13:34]

Hm, we should be using this in more tests above.

[Andrey Kraynov, 2015/12/22 08:38:57]

Don't you mind if I will create a CL to use this pattern in widget_unittest.cc
file?

+
+}
+
+// Ensure scale factor changes are propagated from the native Widget.
+TEST_F(WidgetTest, OnDeviceScaleFactorChanged) {
+  // Automatically close the widget, but not delete it.
+  scoped_ptr<Widget, WidgetCloser> widget(CreateTopLevelPlatformWidget());
+  ScaleFactorView* view = new ScaleFactorView;
+  widget->GetRootView()->AddChildView(view);
+  float scale_factor = widget->GetLayer()->device_scale_factor();
+  EXPECT_NE(scale_factor, 0.f);
+
+  // For views that are not layer-backed, adding the view won't notify the view
+  // about the initial scale factor. Fake it.
+  view->OnDeviceScaleFactorChanged(scale_factor);
+  EXPECT_EQ(scale_factor, view->last_scale_factor());
+
+  // Changes should be propagated.
+  scale_factor *= 2.0f;
+  widget->GetLayer()->OnDeviceScaleFactorChanged(scale_factor);
+  EXPECT_EQ(scale_factor, view->last_scale_factor());
+}
+
 }  // namespace test
 }  // namespace views