MacViews: Handle Space and Return keys correctly for Buttons.

ui/views/style/platform_style_mac.mm

Index: ui/views/style/platform_style_mac.mm
diff --git a/ui/views/style/platform_style_mac.mm b/ui/views/style/platform_style_mac.mm
index 4e07484e09028f50267ef9ee6733c3df515457f9..832e6d81ea26a5d641b45d234bb7d9cc2703be93 100644
--- a/ui/views/style/platform_style_mac.mm
+++ b/ui/views/style/platform_style_mac.mm
@@ -37,6 +37,13 @@
 const CustomButton::NotifyAction PlatformStyle::kMenuNotifyActivationAction =
     CustomButton::NOTIFY_ON_PRESS;
 
+const CustomButton::ButtonAction PlatformStyle::kButtonActionOnSpace =
+    CustomButton::ACTION_CLICK;
+
+// On Mac, the Return Key is used to perform the default action even when a
+// control is focused.
+const bool PlatformStyle::kClickControlOnReturn = false;
+
 // static
 gfx::ImageSkia PlatformStyle::CreateComboboxArrow(bool is_enabled,
                                                   Combobox::Style style) {