Fix back button handling in ACTV

AutoCompleteTextView.onKeyPreIme() used
getKeyDispatcherState().startTracking(event, this) to start tracking
the back button, but didn't update the state of the event
before checking event.isTracking().

Fixes http://b/issue?id=2167168
"AutoCompleteTextView back button handling is broken"

Change-Id: I2c5f1e761872b9e02d85ff6f958fabd558d041a0

core/java/android/widget/AutoCompleteTextView.java

@@ -613,10 +613,12 @@ public class AutoCompleteTextView extends EditText implements Filter.FilterListe
                     && event.getRepeatCount() == 0) {
                 getKeyDispatcherState().startTracking(event, this);
                 return true;
-            } else if (event.getAction() == KeyEvent.ACTION_UP
-                    && event.isTracking() && !event.isCanceled()) {
-                dismissDropDown();
-                return true;
+            } else if (event.getAction() == KeyEvent.ACTION_UP) {
+                getKeyDispatcherState().handleUpEvent(event);
+                if (event.isTracking() && !event.isCanceled()) {
+                    dismissDropDown();
+                    return true;
+                }
             }
         }
         return super.onKeyPreIme(keyCode, event);