Build gpu stats tracking in dev builds.

Fix cache stats, add more info.

BUG=skia:2889

Review URL: https://codereview.chromium.org/655263005
Ignore simpleaaclip_path on Win7-gpu for now.

BUG=skia:3066
TBR=mtklein@google.com

Review URL: https://codereview.chromium.org/646523005
Add harfbuzz to DEPS

https://skia.googlesource.com/third_party/harfbuzz/

BUG=skia:3067

Review URL: https://codereview.chromium.org/679733002
Print GPU cache stats in nanobench/dm with veryVerbose

Review URL: https://codereview.chromium.org/680553002
Remove a pointless use of SkWeakRefCnt.

Can't quite get rid of SkWeakRefCnt yet... SkFontMgr_indirect uses it to cache
SkTypefaces, and I don't quite understand it enough yet to cut out the weak refs.

BUG=skia:3065

Review URL: https://codereview.chromium.org/664173003
move c api into include

BUG=skia:

Review URL: https://codereview.chromium.org/665203004