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

base/platform_file_posix.cc

 // Copyright (c) 2009 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 "base/platform_file.h"
 
 #include <fcntl.h>
 #include <errno.h>
 #include <sys/stat.h>
 
@@ skipping 59 matching lines @@
 
 PlatformFile CreatePlatformFile(const std::wstring& name, int flags,
                                 bool* created) {
   return CreatePlatformFile(FilePath::FromWStringHack(name), flags, created);
 }
 
 bool ClosePlatformFile(PlatformFile file) {
   return close(file);
 }
 
+bool GetPlatformFileSize(PlatformFile file, uint64* out_size) {
+  struct stat st;
+  if (fstat(file, &st))
+    return false;
+  *out_size = st.st_size;
+  return true;
+}
+
 }  // namespace base