change impl to explicitly store length as u32, rather than size_t, so we keep a packed struct on 64bit machines

BUG=

Review URL: https://codereview.chromium.org/16356006

git-svn-id: http://skia.googlecode.com/svn/trunk/include@9436 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed