Don't relayout based on a window that isn't visible

The method commitFinishDrawingLocked returned true even if the window
it was called for was hidden. By returning the value that
performShowLocked() returns it only returns true if the window is
shown.

Fixes bug 19100757.

Change-Id: I45df70aedcb3909561fd3a19e861579a11521db9

services/core/java/com/android/server/wm/WindowStateAnimator.java

@@ -542,9 +542,9 @@ class WindowStateAnimator {
         mDrawState = READY_TO_SHOW;
         final AppWindowToken atoken = mWin.mAppToken;
         if (atoken == null || atoken.allDrawn || mWin.mAttrs.type == TYPE_APPLICATION_STARTING) {
-            performShowLocked();
+            return performShowLocked();
         }
-        return true;
+        return false;
     }
 
     static class SurfaceTrace extends SurfaceControl {