In SkWriter32::writeString, initialize all memory reserved.

SkFlatData compares data which is sometimes created by writeString.
Initialize all the memory in writeString so it does not compare
uninitialized memory.

See http://code.google.com/p/skia/issues/detail?id=721&thanks=721

Review URL: https://codereview.appspot.com/6428054

git-svn-id: http://skia.googlecode.com/svn/trunk@4715 2bbb7eff-a529-9590-31e7-b0007b416f81
2 files changed