Remove needless do-while(false) block from inlined blend methods.

The optimizer still doesn't understand how to remove an unnecessary do-
while loop, but this change will prevent blend_src_in and blend_dst_in
from having an early return at all, and won't otherwise pessimize the
output. This will also allow these blends to be inlined on systems which
don't support do-while loops at all.

Change-Id: I44ef7b3a50571e1a2fe6214f5821ab886471b4aa
Bug: skia:10737
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/318236
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
2 files changed