Cleanup: Simplify some extensions / content_settings Observer code by simply DCHECKING instead of u…

chrome/browser/extensions/api/preference/preference_api.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/api/preference/preference_api.h"
 
 #include <map>
 #include <utility>
 
 #include "base/memory/singleton.h"
@@ skipping 239 matching lines @@
     incognito_registrar_.Add(kPrefMapping[i].browser_pref, this);
   }
 }
 
 PreferenceEventRouter::~PreferenceEventRouter() { }
 
 void PreferenceEventRouter::Observe(
     int type,
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    const std::string* pref_key =
-        content::Details<const std::string>(details).ptr();
-    OnPrefChanged(content::Source<PrefService>(source).ptr(), *pref_key);
-  } else {
-    NOTREACHED();
-  }
+  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
+  OnPrefChanged(content::Source<PrefService>(source).ptr(),
+                *content::Details<const std::string>(details).ptr());
 }
 
 void PreferenceEventRouter::OnPrefChanged(PrefService* pref_service,
                                           const std::string& browser_pref) {
   bool incognito = (pref_service != profile_->GetPrefs());
 
   std::string event_name;
   APIPermission::ID permission = APIPermission::kInvalid;
   bool rv = PrefMapping::GetInstance()->FindEventForBrowserPref(
       browser_pref, &event_name, &permission);
@@ skipping 237 matching lines @@
   if (!ValidateBrowserPref(pref_key, &browser_pref))
     return false;
 
   extensions::ExtensionPrefs* prefs =
       profile_->GetExtensionService()->extension_prefs();
   prefs->RemoveExtensionControlledPref(extension_id(), browser_pref, scope);
   return true;
 }
 
 }  // namespace extensions