Allocate SkPictureFlat::fScratch lazily.

Cuts out half to two thirds of allocations of this object.
Since we're already lazily allocating fWriteBuffer, we don't have to add any other code complexity.

BUG=http://skbug.com/1980
R=mtklein@google.com, tomhudson@google.com

Author: tomhudson@chromium.org

Review URL: https://codereview.chromium.org/131483005

git-svn-id: http://skia.googlecode.com/svn/trunk@12992 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed