Hide wallpaper when wallpaper target gets hidden.

Another location that potentially hides the wallpaper target while
leaving the wallpaper itself still visible. Causes the wallpaper to
show up when upper surfaces are transparent all the way down.

Fixes bug b6621986.

Change-Id: If75053160f041eb78868eda36b7820fb2110d069

Author: Craig Mautner

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

@@ -1067,6 +1067,11 @@ public void prepareSurfaceLocked(final boolean recoveringMemory) {
 
         if (w.mAttachedHidden || !w.isReadyForDisplay()) {
             hide();
+            // TODO: Consider moving the following into hide() and out of finishExit() as well.
+            if (mService.mWallpaperTarget == mWin && mService.mLowerWallpaperTarget == null) {
+                mAnimator.hideWallpapersLocked();
+                mAnimator.mPendingLayoutChanges |= WindowManagerPolicy.FINISH_LAYOUT_REDO_WALLPAPER;
+            }
             // If we are waiting for this window to handle an
             // orientation change, well, it is hidden, so
             // doesn't really matter.  Note that this does