Correct stride for drawing to cached glyph bitmap

fixes the glyph cachebuffer index to account for pixelbuffer
format size.

issue: in launcher home screen create icon group and rename the
group to some text string with emo-icons (smilies). without this
change the drop shadows for emo-icons will look bad.

Change-Id: I525a9219d35f4541363fd64e7fc5fd1053269725
Signed-off-by: Digish Pandya <digishp@codeaurora.org>
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>
Merge remote-tracking branch 'cm/cm-11.0' into cm-11.0