Support returning raw pointers from property getter

A type converter for unique_ptr type should be able to accept a getter
which returns the raw pointer type. This CL adds such support. Also it
adds such a property in ToggleImageButton class as an example.

Bug: 1168309
Change-Id: I49488d475cd70a7441f4f7e5918929c8e5b35638
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2639655Reviewed-by: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Wei Li <weili@chromium.org>
Cr-Commit-Position: refs/heads/master@{#846230}

ash/system/audio/unified_volume_view.cc

@@ -161,7 +161,7 @@ class LiveCaptionButton
     views::SetToggledImageFromVectorIconWithColor(
         this, vector_icons::kLiveCaptionOnIcon, icon_size,
         GetToggledIconColor(), GetToggledIconColor());
-    toggled_background()->SetNativeControlColor(GetToggledBackgroundColor());
+    GetToggledBackground()->SetNativeControlColor(GetToggledBackgroundColor());
   }
 
   SkColor GetToggledIconColor() {

ui/views/controls/button/image_button.cc

@@ -357,6 +357,7 @@ END_METADATA
 
 BEGIN_METADATA(ToggleImageButton, ImageButton)
 ADD_PROPERTY_METADATA(bool, Toggled)
+ADD_PROPERTY_METADATA(std::unique_ptr<Background>, ToggledBackground)
 ADD_PROPERTY_METADATA(base::string16, ToggledTooltipText)
 ADD_PROPERTY_METADATA(base::string16, ToggledAccessibleName)
 END_METADATA

ui/views/controls/button/image_button.h

@@ -141,7 +141,7 @@ class VIEWS_EXPORT ToggleImageButton : public ImageButton {
   // Like Views::SetBackground(), but to set the background color used for the
   // "has been toggled" state.
   void SetToggledBackground(std::unique_ptr<Background> b);
-  Background* toggled_background() { return toggled_background_.get(); }
+  Background* GetToggledBackground() const { return toggled_background_.get(); }
 
   // Get/Set the tooltip text displayed when the button is toggled.
   base::string16 GetToggledTooltipText() const;
@@ -184,6 +184,7 @@ class VIEWS_EXPORT ToggleImageButton : public ImageButton {
 
 BEGIN_VIEW_BUILDER(VIEWS_EXPORT, ToggleImageButton, ImageButton)
 VIEW_BUILDER_PROPERTY(bool, Toggled)
+VIEW_BUILDER_PROPERTY(std::unique_ptr<Background>, ToggledBackground)
 VIEW_BUILDER_PROPERTY(base::string16, ToggledTooltipText)
 VIEW_BUILDER_PROPERTY(base::string16, ToggledAccessibleName)
 END_VIEW_BUILDER

ui/views/metadata/type_conversion.h

@@ -209,6 +209,7 @@ struct TypeConverter<base::Optional<T>>
 template <typename T>
 struct TypeConverter<std::unique_ptr<T>> : BaseTypeConverter<false> {
   static base::string16 ToString(const std::unique_ptr<T>& source_value);
+  static base::string16 ToString(const T* source_value);
   static base::Optional<std::unique_ptr<T>> FromString(
       const base::string16& source_value);
   static ValidStrings GetValidStrings() { return {}; }