[ScreentShot]: change the implementation of get image file size

Because File can't get permission to get file size of screenshot image.
So use InputStream to get file size correctly of screenshot image.

Change-Id: I1c3df40ddd526d3431bc899642d00f4021d7eeb3
Author: Bo Huang <bo.b.huang@intel.com>
Signed-off-by: Bo Huang <bo.b.huang@intel.com>
Signed-off-by: shi yang <yang.a.shi@intel.com>
Signed-off-by: Shuo Gao <shuo.gao@intel.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
Signed-off-by: Jack Ren <jack.ren@intel.com>
Author-tracking-BZ: 30940

Conflicts:
	packages/SystemUI/src/com/android/systemui/screenshot/GlobalScreenshot.java

Signed-off-by: hany <hany.alsamman@gmail.com>