Fix crash in ChromeZoomLevelPrefs::ExtractPerHostZoomLevels().

chrome/browser/ui/zoom/chrome_zoom_level_prefs.cc

 // Copyright 2014 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/ui/zoom/chrome_zoom_level_prefs.h"
 
 #include <sstream>
 
 #include "base/bind.h"
 #include "base/prefs/json_pref_store.h"
@@ skipping 60 matching lines @@
   // Initialize the HostZoomMap with per-host zoom levels from the persisted
   // zoom-level preference values.
   const base::DictionaryValue* host_zoom_dictionaries =
       pref_service_->GetDictionary(prefs::kPartitionPerHostZoomLevels);
   const base::DictionaryValue* host_zoom_dictionary = nullptr;
   if (host_zoom_dictionaries->GetDictionary(partition_key_,
                                             &host_zoom_dictionary)) {
     // Since we're calling this before setting up zoom_subscription_ below we
     // don't need to worry that host_zoom_dictionary is indirectly affected
     // by calls to HostZoomMap::SetZoomLevelForHost().
-    ExtractPerHostZoomLevels(host_zoom_dictionary);
+    ExtractPerHostZoomLevels(host_zoom_dictionary,
+                             true /* sanitize_partition_host_zoom_levels */);
   }
   zoom_subscription_ = host_zoom_map_->AddZoomLevelChangedCallback(base::Bind(
       &ChromeZoomLevelPrefs::OnZoomLevelChanged, base::Unretained(this)));
 }
 
 std::string ChromeZoomLevelPrefs::GetHashForTesting(
     const base::FilePath& relative_path) {
   return GetHash(relative_path);
 }
 
@@ skipping 45 matching lines @@
     host_zoom_dictionary = new base::DictionaryValue();
     host_zoom_dictionaries->Set(partition_key_, host_zoom_dictionary);
   }
 
   if (modification_is_removal)
     host_zoom_dictionary->RemoveWithoutPathExpansion(change.host, nullptr);
   else
     host_zoom_dictionary->SetDoubleWithoutPathExpansion(change.host, level);
 }
 
+// TODO(wjmaclean): Remove the dictionary_path once the migration code is
+// removed. crbug.com/420643
 void ChromeZoomLevelPrefs::ExtractPerHostZoomLevels(
-    const base::DictionaryValue* host_zoom_dictionary) {
+    const base::DictionaryValue* host_zoom_dictionary,
+    bool sanitize_partition_host_zoom_levels) {
   std::vector<std::string> keys_to_remove;
   scoped_ptr<base::DictionaryValue> host_zoom_dictionary_copy(
       host_zoom_dictionary->DeepCopyWithoutEmptyChildren());
   for (base::DictionaryValue::Iterator i(*host_zoom_dictionary_copy);
        !i.IsAtEnd();
        i.Advance()) {
     const std::string& host(i.key());
     double zoom_level = 0;
 
     bool has_valid_zoom_level = i.value().GetAsDouble(&zoom_level);
 
     // Filter out A) the empty host, B) zoom levels equal to the default; and
     // remember them, so that we can later erase them from Prefs.
     // Values of type A and B could have been stored due to crbug.com/364399.
     // Values of type B could further have been stored before the default zoom
     // level was set to its current value. In either case, SetZoomLevelForHost
     // will ignore type B values, thus, to have consistency with HostZoomMap's
     // internal state, these values must also be removed from Prefs.
     if (host.empty() || !has_valid_zoom_level ||
         content::ZoomValuesEqual(zoom_level,
                                  host_zoom_map_->GetDefaultZoomLevel())) {
       keys_to_remove.push_back(host);
       continue;
     }
 
     host_zoom_map_->SetZoomLevelForHost(host, zoom_level);
   }
 
+  // We don't bother sanitizing non-partition dictionaries as they will be
+  // discarded in the migration process. Note: since the structure of partition
+  // per-host zoom level dictionaries is different from the legacy profile
+  // per-host zoom level dictionaries, the following code will fail if run
+  // on the legacy dictionaries.
+  if (!sanitize_partition_host_zoom_levels)
+    return;
+
   // Sanitize prefs to remove entries that match the default zoom level and/or
   // have an empty host.
   {
     DictionaryPrefUpdate update(pref_service_,
                                 prefs::kPartitionPerHostZoomLevels);
     base::DictionaryValue* host_zoom_dictionaries = update.Get();
     base::DictionaryValue* host_zoom_dictionary = nullptr;
     host_zoom_dictionaries->GetDictionary(partition_key_,
                                           &host_zoom_dictionary);
     for (const std::string& s : keys_to_remove)
       host_zoom_dictionary->RemoveWithoutPathExpansion(s, nullptr);
   }
 }
 
 }  // namespace chrome