Fix bug in SkWriter32.

If you give SkWriter32 external storage but that external storage is too small
for the first reservation you make, you'll hit an assert in debug mode.

I think the answer is to simply remove the SkASSERT.  Added a test.

BUG=
R=reed@google.com

Review URL: https://codereview.chromium.org/23646007

git-svn-id: http://skia.googlecode.com/svn/trunk@11062 2bbb7eff-a529-9590-31e7-b0007b416f81
2 files changed