Fix issue #21813831: Need API for asking to be added to power whitelist

Add the API.  Clean up a few related things.

Change-Id: I190adad1812f36f6095b98a1001fedb94874e8b5
diff --git a/core/java/android/provider/Settings.java b/core/java/android/provider/Settings.java
index e335f6d..dfd72c2 100644
--- a/core/java/android/provider/Settings.java
+++ b/core/java/android/provider/Settings.java
@@ -579,13 +579,14 @@
     /**
      * Activity Action: Show screen for controlling which apps can ignore battery optimizations.
      * <p>
-     * In some cases, a matching Activity may not exist, so ensure you
-     * safeguard against this.
-     * <p>
-     * Input: The Intent's data URI specifies the application package name
+     * Input: Optionally, the Intent's data URI specifies the application package name
      * to be shown, with the "package" scheme.  That is "package:com.my.app".
      * <p>
      * Output: Nothing.
+     * <p>
+     * You can use {@link android.os.PowerManager#isIgnoringBatteryOptimizations
+     * PowerManager.isIgnoringBatteryOptimizations()} to determine if an application is
+     * already ignoring optimizations.
      */
     @SdkConstant(SdkConstantType.ACTIVITY_INTENT_ACTION)
     public static final String ACTION_IGNORE_BATTERY_OPTIMIZATION_SETTINGS =