core/jni/android/graphics: Cache copy of pre-scaled Bitmaps

Caching some pre-scaled Bitmap objects allows for optimizing later
scaling operations to reduce memory pressure.

CRs-fixed: 451681

Change-Id: Id4341e75911074ff9f565b2d386ccad8f3a223e8
Merge branch 'cm-10.1' of git://github.com/CyanogenMod/android_frameworks_base into cm-10.1-n7