Improvements to low power mode.

Add new public API for monitoring low power mode.

BatteryService now puts device in to low power mode when
battery level is low.

Window manager now watches low power mode to turn off
animations.

Modifying the animator scale now gets propagated to all
processes.

Change-Id: I8fa566994764ddd4e1977631e28381ab9409f8ee
diff --git a/core/res/AndroidManifest.xml b/core/res/AndroidManifest.xml
index d844818..f57c3a0 100644
--- a/core/res/AndroidManifest.xml
+++ b/core/res/AndroidManifest.xml
@@ -74,6 +74,8 @@
     <protected-broadcast android:name="android.intent.action.USER_FOREGROUND" />
     <protected-broadcast android:name="android.intent.action.USER_SWITCHED" />
 
+    <protected-broadcast android:name="android.os.action.POWER_SAVE_MODE_CHANGED" />
+
     <protected-broadcast android:name="android.app.action.ENTER_CAR_MODE" />
     <protected-broadcast android:name="android.app.action.EXIT_CAR_MODE" />
     <protected-broadcast android:name="android.app.action.ENTER_DESK_MODE" />