Fix "crashed extension" infobar browser crashes.

chrome/browser/extensions/extension_prefs.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 "chrome/browser/extensions/extension_prefs.h"
 
 #include "base/string_util.h"
 #include "chrome/common/extensions/extension.h"
 
 namespace {
@@ skipping 371 matching lines @@
   }
 
   return version;
 }
 
 void ExtensionPrefs::MigrateToPrefs(Extension* extension) {
   UpdateExtensionPref(extension->id(), kPrefManifest,
                       extension->manifest_value()->DeepCopy());
 }
 
+FilePath ExtensionPrefs::GetExtensionPath(const std::string& extension_id) {
+  const DictionaryValue* dict = prefs_->GetDictionary(kExtensionsPref);
+  if (!dict || dict->GetSize() == 0)
+    return FilePath();
+
+  std::wstring path;
+  if (!dict->GetString(ASCIIToWide(extension_id) + L"." + kPrefPath, &path))
+    return FilePath();
+
+  return install_directory_.Append(FilePath::FromWStringHack(path));
+}
+
 bool ExtensionPrefs::UpdateExtensionPref(const std::string& extension_id,
                                          const std::wstring& key,
                                          Value* data_value) {
   DictionaryValue* extension = GetOrCreateExtensionPref(extension_id);
   if (!extension->Set(key, data_value)) {
     NOTREACHED() << "Cannot modify key: '" << key.c_str()
                  << "' for extension: '" << extension_id.c_str() << "'";
     return false;
   }
   return true;
@@ skipping 22 matching lines @@
 }
 
 DictionaryValue* ExtensionPrefs::GetExtensionPref(
     const std::string& extension_id) {
   const DictionaryValue* dict = prefs_->GetDictionary(kExtensionsPref);
   DictionaryValue* extension = NULL;
   std::wstring id = ASCIIToWide(extension_id);
   dict->GetDictionary(id, &extension);
   return extension;
 }