Make notification buttons draw a background so text gets subpixel AA.

ui/message_center/cocoa/notification_controller.mm

 // Copyright (c) 2013 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.
 
 #import "ui/message_center/cocoa/notification_controller.h"
 
 #include "base/mac/foundation_util.h"
 #include "base/strings/string_util.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 34 matching lines @@
 
   path = [NSBezierPath bezierPathWithRoundedRect:sliceRect
       xRadius:message_center::kProgressBarCornerRadius
       yRadius:message_center::kProgressBarCornerRadius];
   [gfx::SkColorToCalibratedNSColor(message_center::kProgressBarSliceColor) set];
   [path fill];
 }
 @end
 
 ////////////////////////////////////////////////////////////////////////////////
+@interface MCNotificationButton : NSButton
+@end
+
+@implementation MCNotificationButton
+// drawRect: needs to fill the button with a background, otherwise we don't get
+// subpixel antialiasing.
+- (void)drawRect:(NSRect)dirtyRect {
+  NSColor* color = gfx::SkColorToCalibratedNSColor(
+      message_center::kNotificationBackgroundColor);
+  [color set];
+  NSRectFill(dirtyRect);
+  [super drawRect:dirtyRect];
+}
+@end
 
 @interface MCNotificationButtonCell : NSButtonCell {
   BOOL hovered_;
 }
 @end
 
+////////////////////////////////////////////////////////////////////////////////
 @implementation MCNotificationButtonCell
+- (BOOL)isOpaque {
+  return YES;
+}
+
 - (void)drawBezelWithFrame:(NSRect)frame inView:(NSView*)controlView {
   // Else mouseEntered: and mouseExited: won't be called and hovered_ won't be
   // valid.
   DCHECK([self showsBorderOnlyWhileMouseInside]);
 
   if (!hovered_)
     return;
   [gfx::SkColorToCalibratedNSColor(
       message_center::kHoveredButtonBackgroundColor) set];
   NSRectFill(frame);
@@ skipping 407 matching lines @@
   bottomView_.reset([[NSView alloc] initWithFrame:frame]);
   CGFloat y = 0;
 
   // Create action buttons if appropriate, bottom-up.
   std::vector<message_center::ButtonInfo> buttons = notification->buttons();
   for (int i = buttons.size() - 1; i >= 0; --i) {
     message_center::ButtonInfo buttonInfo = buttons[i];
     NSRect buttonFrame = frame;
     buttonFrame.origin = NSMakePoint(0, y);
     buttonFrame.size.height = message_center::kButtonHeight;
-    base::scoped_nsobject<NSButton> button(
-        [[NSButton alloc] initWithFrame:buttonFrame]);
+    base::scoped_nsobject<MCNotificationButton> button(
+        [[MCNotificationButton alloc] initWithFrame:buttonFrame]);
     base::scoped_nsobject<MCNotificationButtonCell> cell(
         [[MCNotificationButtonCell alloc]
             initTextCell:base::SysUTF16ToNSString(buttonInfo.title)]);
     [cell setShowsBorderOnlyWhileMouseInside:YES];
     [button setCell:cell];
     [button setImage:buttonInfo.icon.AsNSImage()];
     [button setBezelStyle:NSSmallSquareBezelStyle];
     [button setImagePosition:NSImageLeft];
     [button setTag:i];
     [button setTarget:self];
@@ skipping 279 matching lines @@
     if (gfx::GetStringWidth(last, font_list) > width)
       last = gfx::ElideText(last, font_list, width, gfx::ELIDE_AT_END);
     wrapped.resize(lines - 1);
     wrapped.push_back(last);
   }
 
   return lines == 1 ? wrapped[0] : JoinString(wrapped, '\n');
 }
 
 @end