Description: Fixed the problem that a gallery not turn back to last UI when user executing following steps luncher--press menu--Wallpapers--Gallery--select a picture--press home action bar,this opreation should be back up last select picture screen

Steps: 1. in luncher screen, press menu button.

       2. select Wallpapers item.

       3. select a picture.

       4. press home action bar

Change-Id: I1eeadb225030b27b214b3f32bbf5a232ffd82068
Result:gallery not bact to last ui
Improve efficient usage of WidgetDatabaseHelper in PhotoAppWidgetProvider

when user set to update photo widget frequently,
sqlitehelper class creation will be repeated.
by placing sqlitehelper instance in provider class,
this useless phase can be eliminated.
this patch set is to create a sqlitehelper class only one time.

sqlitehelper creation and destruction is high cost internally.
therefore this patch can improve widget update performance.

Change-Id: If4287e02d3d7a9aa798f7e87161d36f52f44dea8
Force close seen while deleting image
RCA: The MediaItem was set to Null before UpdateContent got executed.

Change-Id: I3213d062ffab9e1fa1bf6db602fc724d2b47ddc7