Send pointerleave and pointerenter events for styluses on Mac

ui/base/cocoa/base_view.mm

 // Copyright (c) 2011 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.
 
 #include "ui/base/cocoa/base_view.h"
 
 #include "base/mac/mac_util.h"
 
 NSString* kViewDidBecomeFirstResponder =
     @"Chromium.kViewDidBecomeFirstResponder";
@@ skipping 64 matching lines @@
   // The default implementation of this method does not handle any key events.
   // Derived classes should return kEventHandled if they handled an event,
   // otherwise it will be forwarded on to |super|.
   return kEventNotHandled;
 }
 
 - (void)forceTouchEvent:(NSEvent*)theEvent {
   // This method left intentionally blank.
 }
 
+- (void)tabletEvent:(NSEvent*)theEvent {
+  // This method left intentionally blank.
+}
+
 - (void)mouseDown:(NSEvent*)theEvent {
   dragging_ = YES;
   [self mouseEvent:theEvent];
 }
 
 - (void)rightMouseDown:(NSEvent*)theEvent {
   [self mouseEvent:theEvent];
 }
 
 - (void)otherMouseDown:(NSEvent*)theEvent {
@@ skipping 98 matching lines @@
   new_rect.set_y(NSHeight([self bounds]) - new_rect.bottom());
   return new_rect;
 }
 
 - (NSRect)flipRectToNSRect:(gfx::Rect)rect {
   NSRect new_rect(NSRectFromCGRect(rect.ToCGRect()));
   new_rect.origin.y = NSHeight([self bounds]) - NSMaxY(new_rect);
   return new_rect;
 }
 
+- (void)tabletProximity:(NSEvent*)theEvent {
+  [self tabletEvent:theEvent];
+}
+
 @end