Better guarantee a11y service initial state

I've see flakiness in the gesture dispatch test with
magnification enabled. It turned out that the state
of the input filter was in flux when onServiceConnected
was called back. Now delaying that call until the
input filter's state is stable.

Also fixing the return value of getCenterX and Y when
a service isn't actively controlling magnification.

Test: A11y CTS and unit tests.
Change-Id: I64260ebb72ee95307d777a9e4b70876c14f99e9c
diff --git a/services/core/java/com/android/server/wm/AccessibilityController.java b/services/core/java/com/android/server/wm/AccessibilityController.java
index 805250a..6484a13 100644
--- a/services/core/java/com/android/server/wm/AccessibilityController.java
+++ b/services/core/java/com/android/server/wm/AccessibilityController.java
@@ -429,6 +429,8 @@
         }
 
         public void getMagnificationRegionLocked(Region outMagnificationRegion) {
+            // Make sure we're working with the most current bounds
+            mMagnifedViewport.recomputeBoundsLocked();
             mMagnifedViewport.getMagnificationRegionLocked(outMagnificationRegion);
         }