provide better instructions for adding settings views.

And provide a ready default constant.

Change-Id: I76c9ee50af5d97f9f83be7b0eb862f73fc9bfa7b
diff --git a/src/com/android/settings/InstrumentedPreferenceActivity.java b/src/com/android/settings/InstrumentedPreferenceActivity.java
index 8ad88b0..480d5c7 100644
--- a/src/com/android/settings/InstrumentedPreferenceActivity.java
+++ b/src/com/android/settings/InstrumentedPreferenceActivity.java
@@ -23,6 +23,13 @@
  * Instrumented activity that logs visibility state.
  */
 public abstract class InstrumentedPreferenceActivity extends PreferenceActivity {
+    /**
+     * Declare the view of this category.
+     *
+     * Categories are defined in {@link com.android.internal.logging.MetricsLogger}
+     * or if there is no relevant existing category you may define one in
+     * {@link com.android.settings.InstrumentedFragment}.
+     */
     protected abstract int getMetricsCategory();
 
     @Override