Use alpha channel instead of red in drawCachedGlyphBitmap

the correct value to copy in bitmap is alpha component from
the cachebuffer. currently it is offset to red channel if format is
RGBA which is wrong.

this is followup fix for https://android-review.googlesource.com/#/c/93943/

Change-Id: I96b5ba35df5ccaef44caf2542d35d6585ba1df80
Signed-off-by: Digish Pandya <digishp@codeaurora.org>
bless python versions newer than 2.6

Change-Id: Ic4bfb857586f1fd4aa9cfddf5984341a89b0cd4a
Signed-off-by: Li Li <lli5@nvidia.com>
Reviewed-on: http://git-master/r/347711
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Peter Zu <pzu@nvidia.com>