Update process importance documentation.

Also be more direct about some of the wallpaper APIs.

Change-Id: I2112898c0cd4415d6c5fd47923de682d59b8291f
diff --git a/core/java/android/content/ComponentCallbacks2.java b/core/java/android/content/ComponentCallbacks2.java
index 85294dd..a3b4e5e 100644
--- a/core/java/android/content/ComponentCallbacks2.java
+++ b/core/java/android/content/ComponentCallbacks2.java
@@ -88,7 +88,11 @@
      * should never compare to exact values of the level, since new intermediate
      * values may be added -- you will typically want to compare if the value
      * is greater or equal to a level you are interested in.
-     * 
+     *
+     * <p>To retrieve the processes current trim level at any point, you can
+     * use {@link android.app.ActivityManager#getMyMemoryState
+     * ActivityManager.getMyMemoryState(RunningAppProcessInfo)}.
+     *
      * @param level The context of the trim, giving a hint of the amount of
      * trimming the application may like to perform.  May be
      * {@link #TRIM_MEMORY_COMPLETE}, {@link #TRIM_MEMORY_MODERATE},