Remove debug-only fData from SKTDArray.

It makes the code harder to read, and makes Debug and Release SkTDArrays
different sizes.  Looks like fData is left over from when debuggers weren't
very good at inspecting data structures.

No API changes.
TBR=reed@google.com

BUG=skia:

Review URL: https://codereview.chromium.org/739263002
1 file changed