Revert 170483 - Remove PrefObserver usages, batch 12.

chrome/browser/ui/ash/launcher/chrome_launcher_controller_per_app.cc

Index: chrome/browser/ui/ash/launcher/chrome_launcher_controller_per_app.cc
===================================================================
--- chrome/browser/ui/ash/launcher/chrome_launcher_controller_per_app.cc	(revision 170518)
+++ chrome/browser/ui/ash/launcher/chrome_launcher_controller_per_app.cc	(working copy)
@@ -173,10 +173,7 @@
                               chrome::NOTIFICATION_EXTENSION_UNLOADED,
                               content::Source<Profile>(profile_));
   pref_change_registrar_.Init(profile_->GetPrefs());
-  pref_change_registrar_.Add(
-      prefs::kPinnedLauncherApps,
-      base::Bind(&ChromeLauncherControllerPerApp::UpdateAppLaunchersFromPref,
-                 base::Unretained(this)));
+  pref_change_registrar_.Add(prefs::kPinnedLauncherApps, this);
 }
 
 ChromeLauncherControllerPerApp::~ChromeLauncherControllerPerApp() {
@@ -230,20 +227,10 @@
     SetShelfAutoHideBehaviorFromPrefs();
     SetShelfAlignmentFromPrefs();
     PrefService* prefs = profile_->GetPrefs();
-    if (prefs->GetString(prefs::kShelfAlignmentLocal).empty()) {
-      pref_change_registrar_.Add(
-          prefs::kShelfAlignmentLocal,
-          base::Bind(
-              &ChromeLauncherControllerPerApp::SetShelfAlignmentFromPrefs,
-              base::Unretained(this)));
+    if (prefs->GetString(prefs::kShelfAlignmentLocal).empty() ||
+        prefs->GetString(prefs::kShelfAutoHideBehaviorLocal).empty()) {
+      prefs->AddObserver(this);
     }
-    if (prefs->GetString(prefs::kShelfAutoHideBehaviorLocal).empty()) {
-      pref_change_registrar_.Add(
-          prefs::kShelfAutoHideBehaviorLocal,
-          base::Bind(&ChromeLauncherControllerPerApp::
-                         SetShelfAutoHideBehaviorFromPrefs,
-                     base::Unretained(this)));
-    }
     ash::Shell::GetInstance()->AddShellObserver(this);
   }
 }
@@ -796,6 +783,20 @@
   }
 }
 
+void ChromeLauncherControllerPerApp::OnPreferenceChanged(
+    PrefServiceBase* service,
+    const std::string& pref_name) {
+  if (pref_name == prefs::kPinnedLauncherApps) {
+    UpdateAppLaunchersFromPref();
+  } else if (pref_name == prefs::kShelfAlignmentLocal) {
+    SetShelfAlignmentFromPrefs();
+  } else if (pref_name == prefs::kShelfAutoHideBehaviorLocal) {
+    SetShelfAutoHideBehaviorFromPrefs();
+  } else {
+    NOTREACHED() << "Unexpected pref change for " << pref_name;
+  }
+}
+
 void ChromeLauncherControllerPerApp::OnShelfAlignmentChanged() {
   const char* pref_value = NULL;
   // TODO(oshima): Support multiple displays.
@@ -864,10 +865,7 @@
       }
     }
   }
-  pref_change_registrar_.Add(
-      prefs::kPinnedLauncherApps,
-      base::Bind(&ChromeLauncherControllerPerApp::UpdateAppLaunchersFromPref,
-                 base::Unretained(this)));
+  pref_change_registrar_.Add(prefs::kPinnedLauncherApps, this);
 }
 
 ash::LauncherModel* ChromeLauncherControllerPerApp::model() {