Fix the case where the browser livelocks if we cannot open a file.

base/platform_file.h

 // Copyright (c) 2006-2008 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 BASE_PLATFORM_FILE_H_
 #define BASE_PLATFORM_FILE_H_
 
 #include "build/build_config.h"
+#include "base/basictypes.h"
+
 #if defined(OS_WIN)
 #include <windows.h>
 #endif
 
 #include <string>
 
 class FilePath;
 
 namespace base {
 
@@ skipping 27 matching lines @@
                                 int flags,
                                 bool* created);
 // Deprecated.
 PlatformFile CreatePlatformFile(const std::wstring& name,
                                 int flags,
                                 bool* created);
 
 // Closes a file handle
 bool ClosePlatformFile(PlatformFile file);
 
+// Get the length of an underlying file. Returns false on error. Otherwise
+// *size is set to the length of the file, in bytes.
+bool GetPlatformFileSize(PlatformFile file, uint64* size);
+
 }  // namespace base
 
 #endif  // BASE_PLATFORM_FILE_H_