Idle maintenance scheduling broken.

1. The scheduling was relying on receiving battery level broadcasts
   which however are not sent if the device is asleep. The maintenance
   window was not bound and we could miss a frame if the user did
   not interact the device longer than the min time between two
   maintenance windows.

2. Hide the idle maintenance intents since this will be rewritten
   to user services.

bug:8688454

Change-Id: I17b421b09823cb46ec218cabda19e02432d94f8c
diff --git a/core/java/android/content/Intent.java b/core/java/android/content/Intent.java
index 67bd952..bfc7bf5 100644
--- a/core/java/android/content/Intent.java
+++ b/core/java/android/content/Intent.java
@@ -2356,6 +2356,8 @@
      * </p>
      *
      * @see #ACTION_IDLE_MAINTENANCE_END
+     *
+     * @hide
      */
     @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)
     public static final String ACTION_IDLE_MAINTENANCE_START =
@@ -2383,6 +2385,8 @@
      * by the system.
      *
      * @see #ACTION_IDLE_MAINTENANCE_START
+     *
+     * @hide
      */
     @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)
     public static final String ACTION_IDLE_MAINTENANCE_END =