MacViews: Handle Space and Return keys correctly for Buttons.

ui/views/style/platform_style.h

 // Copyright 2015 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.
 
 #ifndef UI_VIEWS_STYLE_PLATFORM_STYLE_H_
 #define UI_VIEWS_STYLE_PLATFORM_STYLE_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 28 matching lines @@
 
   // Whether the default button for a dialog can be the Cancel button.
   static const bool kDialogDefaultButtonCanBeCancel;
 
   // Whether right clicking on text, selects the word under cursor.
   static const bool kSelectWordOnRightClick;
 
   // The menu button's action to show the menu.
   static const CustomButton::NotifyAction kMenuNotifyActivationAction;
 
+  // Click action to perform on a button when the Space key is pressed.

[tapted, 2017/01/05 00:34:41]

This comment doesn't read quite right, since "pressed" implies only one side of
the action.

Maybe something like

// Whether the space key clicks a button on key press or key release.

[karandeepb, 2017/01/05 10:50:09]

Done.

+  static const CustomButton::ClickAction kClickActionOnSpace;
+
+  // Whether Return key clicks the focused control.

[tapted, 2017/01/05 00:34:41]

It might be good to be explicit here too. E.g. 

"Whether the Return key clicks the focused control (on key press). Otherwise,
Return does nothing unless it is handled by an accelerator."

(actually on Mac, it should NSBeep() if not handled by an accelerator, but
that's orthogonal)

[karandeepb, 2017/01/05 10:50:09]

Done.

+  static const bool kReturnClicksFocusedControl;
+
   // Whether TreeViews get a focus ring on the entire TreeView when focused.
   static const bool kTreeViewHasFocusRing;
 
   // Whether selecting a row in a TreeView selects the entire row or only the
   // label for that row.
   static const bool kTreeViewSelectionPaintsEntireRow;
 
   // Whether ripples should be used for visual feedback on control activation.
   static const bool kUseRipples;
 
@@ skipping 29 matching lines @@
   // the failed edit if platform-appropriate.
   static void OnTextfieldEditFailed();
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PlatformStyle);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_STYLE_PLATFORM_STYLE_H_