wallpaper: limit wallpaper width to sys.max_texture_size

Image wallpapers are created ~1.5x screen size.  On some devices this
may exceed the maximum supported texture size, which will either fail
allocation or fail to composite.

https://android-review.googlesource.com/95111

Bug 991597

Change-Id: I9948b09f6e00a724212e73d36901f2bbea42e2f4
Signed-off-by: houst0nn <houstonn@gmail.com>
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>
Signed-off-by: houst0nn <houstonn@gmail.com>

Conflicts:
	libs/hwui/font/Font.cpp