ImageWallpaper : get bitmap width before calc screen offset

Inside drawFrameLocked, updateWallpaperLocked() is called after
calculae drawing offset using mBackgroundWidth/Height. Because
mBackgroundWidth/Height is modified inside updateWallpaperLocked(),
it sould be called before Mbackgroundwidth/Height is used.

Many market launcher and some phone vendor launcher call
suggestDesiredDimenstions with argument (w,h) instead aosp's
original (w*2,h) for single page wallpaper. In that case, when
launcher orientation changed, ImageWallpaper does not properly
display wallpaper image and mostly you can see Black Edge at
left.

Change-Id: I93ebc4337b01f73d3154346943afa4afd6b1988a