Add Null check for kExtensionsPref dictionary...

chrome/browser/extensions/extension_prefs.cc

 // Copyright (c) 2011 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 "base/string_number_conversions.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/extensions/extension_pref_store.h"
@@ skipping 1126 matching lines @@
   int64 install_time_i64 = 0;
   if (!base::StringToInt64(install_time_str, &install_time_i64))
     return base::Time();
   return base::Time::FromInternalValue(install_time_i64);
 }
 
 void ExtensionPrefs::GetExtensions(ExtensionIdSet* out) const {
   CHECK(out);
   const DictionaryValue* extensions =
       pref_service()->GetDictionary(kExtensionsPref);
+  if (!extensions)
+    return;

[Mattias Nissler (ping if slow), 2011/01/28 09:27:03]

Hm. I'd say that the problem is really with the PrefService code which shouldn't
return NULL in any case here. Could we resolve the report also by replacing this
code in PrefService::GetDictionary():

  const Value* value = pref->GetValue();
  if (value->GetType() == Value::TYPE_NULL)
    return NULL;
  return static_cast<const DictionaryValue*>(value);

by 

  const Value* value = pref->GetValue();
  CHECK(value->IsType(Value::TYPE_DICTIONARY))
  return static_cast<const DictionaryValue*>(value);

[Aaron Boodman, 2011/01/29 19:24:04]

cpu, did you find a case of this actually returning NULL, or did coverity flag
this?

Mattias, what happens if the Preferences file gets changed by hand and the
extensions key gets replaced with some other type? Will PrefService return a
default DictionaryValue or will it return NULL?

 
   for (DictionaryValue::key_iterator ext_id = extensions->begin_keys();
        ext_id != extensions->end_keys(); ++ext_id) {
     out->push_back(*ext_id);
   }
 }
 
 void ExtensionPrefs::FixMissingPrefs(const ExtensionIdSet& extension_ids) {
   // Fix old entries that did not get an installation time entry when they
   // were installed or don't have a preferences field.
@@ skipping 88 matching lines @@
 void ExtensionPrefs::RegisterUserPrefs(PrefService* prefs) {
   prefs->RegisterDictionaryPref(kExtensionsPref);
   prefs->RegisterListPref(kExtensionToolbar);
   prefs->RegisterIntegerPref(prefs::kExtensionToolbarSize, -1);
   prefs->RegisterDictionaryPref(kExtensionsBlacklistUpdate);
   prefs->RegisterListPref(prefs::kExtensionInstallAllowList);
   prefs->RegisterListPref(prefs::kExtensionInstallDenyList);
   prefs->RegisterListPref(prefs::kExtensionInstallForceList);
   prefs->RegisterStringPref(kWebStoreLogin, std::string() /* default_value */);
 }