remove bogus assert, and remove outdated #ifdef

remove bogus assert, and remove outdated #ifdef

BUG=https://code.google.com/p/skia/issues/detail?id=1820
R=robertphillips@google.com

Committed: https://code.google.com/p/skia/source/detail?r=12196

[reed1, 2013-11-08 16:13:51]

All of the code being removed was leftover from an experiment, where we did not
first initialize the device, and assumed the blitter would (over)write all of
the pixels.

This is no longer true: we do init the buffer first, and this has proved faster.

[robertphillips, 2013-11-08 16:44:00]

lgtm

[reed1, 2013-11-08 17:50:21]

Committed patchset #1 manually as r12196 (presubmit successful).

[epoger, 2013-11-08 17:54:27]

I take it this is a fix for https://code.google.com/p/skia/issues/detail?id=1820
('SkBlitter_A8 assertion failure on Test-Android-Xoom-Tegra2-Arm7-Debug
builder') ?