Add keyboard accessibility to ConstrainedWindowButton

chrome/browser/ui/cocoa/constrained_window/constrained_window_button.mm

Index: chrome/browser/ui/cocoa/constrained_window/constrained_window_button.mm
diff --git a/chrome/browser/ui/cocoa/constrained_window/constrained_window_button.mm b/chrome/browser/ui/cocoa/constrained_window/constrained_window_button.mm
index 9ea5fe9033078ebe66ba7cb3255fa80418f95bd4..8a981da83f6d67f3d317a72d1fecc9b60ebee62b 100644
--- a/chrome/browser/ui/cocoa/constrained_window/constrained_window_button.mm
+++ b/chrome/browser/ui/cocoa/constrained_window/constrained_window_button.mm
@@ -4,6 +4,8 @@
 
 #import "chrome/browser/ui/cocoa/constrained_window/constrained_window_button.h"
 
+#import <Carbon/Carbon.h>  // kVK_Return.
+
 #include "base/mac/scoped_nsobject.h"
 #import "chrome/browser/ui/cocoa/key_equivalent_constants.h"
 #include "skia/ext/skia_utils_mac.h"
@@ -245,6 +247,20 @@ void DrawBorder(const NSRect& frame,
   [path stroke];
 }
 
+- (BOOL)canBecomeKeyView {
+  return YES;
+}
+
+- (void)keyDown:(NSEvent*)event {
+  // Since there is no default button in the bubble, it is safe to activate
+  // all buttons on Enter as well, and be consistent with the Windows
+  // implementation.
+  if ([event keyCode] == kVK_Return)

[Robert Sesek, 2016/03/25 20:16:03]

Return is not typically how buttons are invoked on OS X, it's usually space.
Does that work without this change to -keyDown:?

[juncai, 2016/03/25 20:31:54]

The space works without this change to -keyDown:. So this method is removed.

Done.

+    [self performClick:self];
+  else
+    [super keyDown:event];
+}
+
 @end
 
 @implementation ConstrainedWindowButtonCell