Don't start a dimming operation when hiding.

Check to see if app token is hiding before going ahead with turning on
dimming. Before this fix went in we were turning dimming back on right
after turning it off. Then we didn't turn it off again until all
animations had completed leading to a delayed dim-off experience.

Fixes bug 6378033.

Change-Id: Ic819a0093ba95f62df369266c07525835703c5fa

Author: Craig Mautner

services/java/com/android/server/wm/WindowManagerService.java

@@ -8172,7 +8172,8 @@ private void handleNotObscuredLocked(final WindowState w, final long currentTime
             // so we want to leave all of them as undimmed (for
             // performance reasons).
             mInnerFields.mObscured = true;
-        } else if (canBeSeen && (attrFlags & FLAG_DIM_BEHIND) != 0) {
+        } else if (canBeSeen && (attrFlags & FLAG_DIM_BEHIND) != 0
+                && !(w.mAppToken != null && w.mAppToken.hiddenRequested)) {
             if (localLOGV) Slog.v(TAG, "Win " + w + " obscured=" + mInnerFields.mObscured);
             if (!mInnerFields.mDimming) {
                 //Slog.i(TAG, "DIM BEHIND: " + w);