mac: Remove a workaround that's no longer needed.

content/common/mac/font_loader.mm

 // Copyright (c) 2012 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 "content/common/mac/font_loader.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include <limits>
 
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/logging.h"
 #include "base/mac/foundation_util.h"
 #include "base/mac/scoped_cftyperef.h"
 #include "base/mac/scoped_nsobject.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/threading/thread_restrictions.h"
 #include "content/common/mac/font_descriptor.h"
 
 #include <map>
 
-extern "C" {
-
-// Work around http://crbug.com/93191, a really nasty memory smasher bug.
-// On Mac OS X 10.7 ("Lion"), ATS writes to memory it doesn't own.
-// SendDeactivateFontsInContainerMessage, called by ATSFontDeactivate,
-// may trash memory whenever dlsym(RTLD_DEFAULT,
-// "_CTFontManagerUnregisterFontForData") returns NULL. In that case, it tries
-// to locate that symbol in the CoreText framework, doing some extremely
-// sloppy string handling resulting in a likelihood that the string
-// "Text.framework/Versions/A/CoreText" will be written over memory that it
-// doesn't own. The kicker here is that Apple dlsym always inserts its own
-// leading underscore, so ATS actually winds up looking up a
-// __CTFontManagerUnregisterFontForData symbol, which doesn't even exist in
-// CoreText. It's only got the single-underscore variant corresponding to an
-// underscoreless extern "C" name.
-//
-// Providing a single-underscored extern "C" function by this name results in
-// a __CTFontManagerUnregisterFontForData symbol that, as long as it's public
-// (not private extern) and unstripped, ATS will find. If it finds it, it
-// avoids making amateur string mistakes that ruin everyone else's good time.
-//
-// Since ATS wouldn't normally be able to call this function anyway, it's just
-// left as a no-op here.
-//
-// This file seems as good as any other to place this function. It was chosen
-// because it already interfaces with ATS for other reasons.
-//
-// SendDeactivateFontsInContainerMessage on 10.6 ("Snow Leopard") appears to
-// share this bug but this sort of memory corruption wasn't detected until
-// 10.7. The implementation in 10.5 ("Leopard") does not have this problem.
-__attribute__((visibility("default")))
-void _CTFontManagerUnregisterFontForData(NSUInteger, int) {
-}
-
-}  // extern "C"
-
 namespace {
 
 uint32_t GetFontIDForFont(const base::FilePath& font_path) {
   // content/common can't depend on content/browser, so this cannot call
   // BrowserThread::CurrentlyOn(). Check this is always called on the same
   // thread.
   static pthread_t thread_id = pthread_self();
   DCHECK_EQ(pthread_self(), thread_id);
 
   // Font loading used to call ATSFontGetContainer()
@@ skipping 103 matching lines @@
   if (!provider)
     return false;
 
   *out = CGFontCreateWithDataProvider(provider.get());
 
   if (*out == NULL)
     return false;
 
   return true;
 }