Move dumpJSON behind the SK_ENABLE_DUMP_GPU flag

This should trim the code size of a WASM CanvasKit by 10-20KB.

Bug: skia:
Change-Id: Ibf0f8596c04e891e8f7cbc2fa4f1d1852f7cb462
Reviewed-on: https://skia-review.googlesource.com/c/159261
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
11 files changed