Reland r223124: Don't clear existing extension-defined preferences and content settings when reload…

chrome/browser/extensions/extension_pref_value_map.cc

 // Copyright (c) 2012 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_pref_value_map.h"
 
 #include "base/prefs/pref_value_map.h"
 #include "base/stl_util.h"
 #include "base/values.h"
 
@@ skipping 98 matching lines @@
   ExtensionEntryMap::const_iterator winner =
       GetEffectivePrefValueController(pref_key, incognito, from_incognito);
   if (winner == entries_.end())
     return false;
   return winner->first == extension_id;
 }
 
 void ExtensionPrefValueMap::RegisterExtension(const std::string& ext_id,
                                               const base::Time& install_time,
                                               bool is_enabled) {
-  if (entries_.find(ext_id) != entries_.end())
-    UnregisterExtension(ext_id);
-  entries_[ext_id] = new ExtensionEntry;
-  entries_[ext_id]->install_time = install_time;
+  if (entries_.find(ext_id) == entries_.end()) {
+    entries_[ext_id] = new ExtensionEntry;
+
+    // Only update the install time if the extension is newly installed.
+    entries_[ext_id]->install_time = install_time;
+  }
+
   entries_[ext_id]->enabled = is_enabled;
 }
 
 void ExtensionPrefValueMap::UnregisterExtension(const std::string& ext_id) {
   ExtensionEntryMap::iterator i = entries_.find(ext_id);
   if (i == entries_.end())
     return;
   std::set<std::string> keys;  // keys set by this extension
   GetExtensionControlledKeys(*(i->second), &keys);
 
@@ skipping 222 matching lines @@
 
 void ExtensionPrefValueMap::NotifyPrefValueChanged(const std::string& key) {
   FOR_EACH_OBSERVER(ExtensionPrefValueMap::Observer, observers_,
                     OnPrefValueChanged(key));
 }
 
 void ExtensionPrefValueMap::NotifyOfDestruction() {
   FOR_EACH_OBSERVER(ExtensionPrefValueMap::Observer, observers_,
                     OnExtensionPrefValueMapDestruction());
 }