Cleanup: Go with SkDebugf instead of GrPrintf.

Since GrPrintf is just defined to SkDebugf, we can go with the later
directly.

BUG=None
TEST=None
R=bsalomon@google.com

Review URL: https://codereview.chromium.org/695663003
Quick and dirty test to call the C interface from GO.

BUG=skia:

Review URL: https://codereview.chromium.org/670303005
Objects should be unrefed instead of deleted

When an error occurs reading a flattenable object, it should be unrefed instead of deleted because, in the case of SkXferMode, for example, we'd actually be deleting a cached object kept in a static array.

BUG=428789

Review URL: https://codereview.chromium.org/695633003
Rebaseline GMs for https://codereview.chromium.org/687283002/

BUG=skia:2935

Review URL: https://codereview.chromium.org/684833003
SK_USE_SCALED_FONTMETRICS for correct scaling

related blink change:
https://codereview.chromium.org/691133002

Review URL: https://codereview.chromium.org/692083002
small fix for cache clear

BUG=skia:

Review URL: https://codereview.chromium.org/695873002