Hide the "Set Wallpaper" action bar when clicked.

This already happens everywhere except for the case where an external
app such as Photos started the wallpaper picker. So not only is this
more consistent, it also prevents crashes and other potential issues
caused by clicking "Set Wallpaper" too many times.

Bug: 25026717

Change-Id: I63c6a0ce68656e6e68094e88074a836d8c1034f9
diff --git a/WallpaperPicker/src/com/android/launcher3/WallpaperCropActivity.java b/WallpaperPicker/src/com/android/launcher3/WallpaperCropActivity.java
index b717b59..9af5f16 100644
--- a/WallpaperPicker/src/com/android/launcher3/WallpaperCropActivity.java
+++ b/WallpaperPicker/src/com/android/launcher3/WallpaperCropActivity.java
@@ -123,6 +123,7 @@
                 new View.OnClickListener() {
                     @Override
                     public void onClick(View v) {
+                        actionBar.hide();
                         boolean finishActivityWhenDone = true;
                         // Never fade on finish because we return to the app that started us (e.g.
                         // Photos), not the home screen.