Bring up fast user switcher on right-click of the avatar menu on Mac.

chrome/browser/ui/cocoa/profiles/avatar_button.mm

+// 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.
+
+#import "chrome/browser/ui/cocoa/profiles/avatar_button.h"
+
+@interface AvatarButton (Private)
+
+- (void)rightMouseDown:(NSEvent*)event;
+- (void)performRightClick;
+
+@end
+
+@implementation AvatarButton
+
+// Override rightMouseDown and implement a custom mouse tracking loop.
+- (void)rightMouseDown:(NSEvent*)event {
+  NSEvent* nextEvent = event;
+  BOOL mouseInBounds = NO;
+  hoverState_ = kHoverStateMouseDown;
+
+  do {
+    mouseInBounds = NSPointInRect(
+        [self convertPoint:[nextEvent locationInWindow] fromView:nil],
+        [self convertRect:[self frame] fromView:nil]);
+
+    nextEvent = [[self window]
+        nextEventMatchingMask:NSRightMouseDraggedMask |
+                              NSRightMouseUpMask];
+  } while (NSRightMouseUp != [nextEvent type]);
+
+  hoverState_ = kHoverStateNone;
+
+  if (mouseInBounds) {
+    hoverState_ = kHoverStateMouseOver;
+    [self performRightClick];
+  }
+}
+
+- (void)performRightClick {
+  [[super target] performSelector:rightAction withObject:self];
+}
+
+- (void)setRightAction:(SEL)selector {
+  rightAction = selector;
+}
+
+@end