MenuButton: support Mac look & feel

ui/views/style/platform_style.cc

Index: ui/views/style/platform_style.cc
diff --git a/ui/views/style/platform_style.cc b/ui/views/style/platform_style.cc
index 9027c6632dd0f0365d3ca45922c63e357c996c3c..dc49691d9a110b10a6733f87cb65f89c1aa6f98f 100644
--- a/ui/views/style/platform_style.cc
+++ b/ui/views/style/platform_style.cc
@@ -56,6 +56,16 @@ std::unique_ptr<Background> PlatformStyle::CreateComboboxBackground() {
 }
 
 // static
+std::unique_ptr<Background> PlatformStyle::CreateMenuButtonBackground() {
+  return nullptr;
+}
+
+// static
+std::unique_ptr<FocusableBorder> PlatformStyle::CreateMenuButtonBorder() {
+  return base::WrapUnique(new FocusableBorder());
+}
+
+// static
 std::unique_ptr<LabelButtonBorder> PlatformStyle::CreateLabelButtonBorder(
     Button::ButtonStyle style) {
   if (!ui::MaterialDesignController::IsModeMaterial() ||
@@ -70,6 +80,12 @@ std::unique_ptr<LabelButtonBorder> PlatformStyle::CreateLabelButtonBorder(
 }
 
 // static
+gfx::ImageSkia PlatformStyle::CreateMenuButtonArrow(bool is_enabled) {
+  ui::ResourceBundle& rb = ui::ResourceBundle::GetSharedInstance();
+  return *rb.GetImageSkiaNamed(IDR_MENU_DROPARROW);
+}
+
+// static
 std::unique_ptr<ScrollBar> PlatformStyle::CreateScrollBar(bool is_horizontal) {
   return base::WrapUnique(new NativeScrollBar(is_horizontal));
 }
@@ -83,6 +99,29 @@ SkColor PlatformStyle::TextColorForButton(
 
 #endif  // OS_MACOSX
 
+// This definition is used even on Mac, but Mac has its own
+// CreateComboboxArrow() so it will return something different on Mac.
+// static
+int PlatformStyle::GetComboboxArrowWidth(Combobox::Style style) {
+  const int kNormalLeftPadding = 7;
+  const int kNormalRightPadding = 7;

[tapted, 2016/04/21 06:06:46]

I think we can collapse the left/right and just call it kNormalPadding. Same for
Action. Then multiply by 2. Same below.

[Elly Fong-Jones, 2016/04/21 15:30:27]

Done.

+  const int kActionLeftPadding = 11;
+  const int kActionRightPadding = 12;
+  int padding = style == Combobox::STYLE_NORMAL
+                    ? kNormalLeftPadding + kNormalRightPadding
+                    : kActionLeftPadding + kActionRightPadding;
+  int image_width = CreateComboboxArrow(true, style).size().width();
+  return padding + image_width;
+}
+
+// static
+int PlatformStyle::GetMenuButtonArrowWidth() {
+  const int kLeftPadding = 7;
+  const int kRightPadding = 7;
+  return kLeftPadding + kRightPadding +
+         CreateMenuButtonArrow(true).size().width();
+}
+
 #if !defined(DESKTOP_LINUX) && !defined(OS_MACOSX)
 // static
 void PlatformStyle::ApplyLabelButtonTextStyle(