Productionize PathKit

 - Remove some old API with VerbArgs that we didn't really like.
 - move from experimental/wasm -> experimental/pathkit and rename
wasm_main.cpp to pathkit_wasm_bindings (more descriptive).
 - Make compile.sh nicer to use (with some form of command line args).
 - Use MODULARIZE=1 to make this play nicer with other WASM libraries
and easier to import.
 - Add seperate ToCanvas() API
 - Move Region stuff behind the PATHKIT_TESTING flag (saves 100k on
binary size).
 - Add npm package for wasm version.  asm.js version should also be
supported for older browsers.
 - Remove shell.html, which was largely too complicated. Replace it with
example.html, which is more succinct and demos the more relevant APIs.

See https://www.npmjs.com/package/experimental-pathkit-wasm

Bug: skia:8216
Change-Id: I15f14dd8acd77331729998ae3e30d73e4b006761
Reviewed-on: https://skia-review.googlesource.com/144790
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
12 files changed