[canvaskit] Refactor Canvas2D JS into own files

Rather than one monolithic file, we now have one monolithic
file (canvascontext2d) and several smaller files (one per class,
and some helpers).

This should make the code navigation a little easier.

Bug: skia:
Change-Id: Ia191c2db778591af21d2a6126f053c17c4f677f1
Reviewed-on: https://skia-review.googlesource.com/c/175996
Reviewed-by: Florin Malita <fmalita@chromium.org>

Author: kjlubick

experimental/canvaskit/compile.sh

@@ -80,7 +80,17 @@ if [[ $@ == *no_managed_skottie* ]]; then
   WASM_MANAGED_SKOTTIE="-DSK_INCLUDE_MANAGED_SKOTTIE=0"
 fi
 
-HTML_CANVAS_API="--pre-js $BASE_DIR/htmlcanvas/canvas2d.js"
+HTML_CANVAS_API="--pre-js $BASE_DIR/htmlcanvas/preamble.js \
+--pre-js $BASE_DIR/htmlcanvas/util.js \
+--pre-js $BASE_DIR/htmlcanvas/color.js \
+--pre-js $BASE_DIR/htmlcanvas/font.js \
+--pre-js $BASE_DIR/htmlcanvas/canvas2dcontext.js \
+--pre-js $BASE_DIR/htmlcanvas/htmlcanvas.js \
+--pre-js $BASE_DIR/htmlcanvas/imagedata.js \
+--pre-js $BASE_DIR/htmlcanvas/lineargradient.js \
+--pre-js $BASE_DIR/htmlcanvas/pattern.js \
+--pre-js $BASE_DIR/htmlcanvas/radialgradient.js \
+--pre-js $BASE_DIR/htmlcanvas/postamble.js "
 if [[ $@ == *no_canvas* ]]; then
   echo "Omitting bindings for HTML Canvas API"
   HTML_CANVAS_API=""

experimental/canvaskit/htmlcanvas/_namedcolors.js

@@ -1,6 +1,6 @@
 // This node script is meant to pre-compute the named colors.
 // node ./htmlcanvas/_namedcolors.js --expose-wasm
-// Put the result in canvas2d.js
+// Put the result in color.js
 // This should likely never need to be re-run.
 
 const CanvasKitInit = require('../canvaskit/bin/canvaskit.js');