Fix for the font files being maped multiple times (Fontconfig).

content/common/font_config_ipc_linux.h

 // 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.
 
 #ifndef CONTENT_COMMON_FONT_CONFIG_IPC_LINUX_H_
 #define CONTENT_COMMON_FONT_CONFIG_IPC_LINUX_H_
 
 #include "base/compiler_specific.h"
+#include "base/containers/hash_tables.h"
+#include "base/synchronization/lock.h"
 #include "third_party/skia/include/ports/SkFontConfigInterface.h"
 
 #include <string>
 
 namespace content {
 
 // FontConfig implementation for Skia that proxies out of process to get out
 // of the sandbox. See http://code.google.com/p/chromium/wiki/LinuxSandboxIPC
 class FontConfigIPC : public SkFontConfigInterface {
  public:
@@ skipping 11 matching lines @@
   enum Method {
     METHOD_MATCH = 0,
     METHOD_OPEN = 1,
   };
 
   enum {
     kMaxFontFamilyLength = 2048
   };
 
  private:
+  class MappedFontFile;
+  friend class MappedFontFile;

[Daniel Erat, 2015/01/14 23:40:27]

(mostly a note for myself: i initially thought that this 'friend' would be
unnecessary, but apparently this is a bug that was addressed in c++11)

[Krzysztof Olczyk, 2015/01/15 09:05:28]

Oh, I wasn't aware it was addressed in C++11, thanks for noting. I will remove
this "friend" as all toolchains are C++11 now.

[Daniel Erat, 2015/01/15 15:55:54]

sorry, i meant it the other way around: apparently nested classes automatically
got access to their outer class's members before, but maybe don't now. (if the
bots compile without 'friend', though, feel free to leave it out!)

[Krzysztof Olczyk, 2015/01/15 17:44:11]

I think it's other way round. I'm pretty sure friend was needed in C++03, but 
looks like it is no longer needed in C++11. 
Bots do compile.  

+
+  // Removes |mapped_font_file| from |mapped_font_files_|.
+  // Does not delete the passed-in object.
+  void RemoveMappedFontFile(MappedFontFile* mapped_font_file);
+
   const int fd_;
+  // Lock preventing multiple threads from opening font file and accessing
+  // |mapped_font_files_| map at the same time.
+  base::Lock stream_opening_lock_;

[Daniel Erat, 2015/01/14 23:40:27]

nit: just rename this to |lock_| since it protects the map in addition to
stream-opening?

[Krzysztof Olczyk, 2015/01/15 09:05:28]

Done.

+  // Maps font identity ID to the memory-mapped file with font data.
+  base::hash_map<uint32_t, MappedFontFile*> mapped_font_files_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_FONT_CONFIG_IPC_LINUX_H_