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>
diff --git a/experimental/pathkit/npm-wasm/LICENSE b/experimental/pathkit/npm-wasm/LICENSE
new file mode 100644
index 0000000..20c685b
--- /dev/null
+++ b/experimental/pathkit/npm-wasm/LICENSE
@@ -0,0 +1,190 @@
+   Copyright 2018 Google LLC
+
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+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
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+
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+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
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diff --git a/experimental/pathkit/npm-wasm/README.md b/experimental/pathkit/npm-wasm/README.md
new file mode 100644
index 0000000..2f02e51
--- /dev/null
+++ b/experimental/pathkit/npm-wasm/README.md
@@ -0,0 +1,54 @@
+A WASM version of Skia's PathOps toolkit.
+
+To use the library, run `npm install experimental-pathkit-wasm` and then simply include it:
+
+    <script src="/node_modules/experimental-pathkit-wasm/bin/pathkit.js"></script>
+    PathKitInit({
+        locateFile: (file) => '/node_modules/experimental-pathkit-wasm/bin/'+file,
+    }).then((PathKit) => {
+        // Code goes here using PathKit
+    });
+
+PathKit comes in two parts, a JS loader and the actual WASM code. The JS loader creates
+a global `PathKitInit` that can be called to load the WASM code. The `locateFile` function
+is used to tell the JS loader where to find the .wasm file. By default, it will
+look for /pathkit.wasm, so if this is not the case, use `locateFile` to configure
+this properly.
+The `PathKit` object returned through the .then() callback is fully loaded and ready to use.
+
+See example.html for a fuller example of how to use the library.
+
+Using PathKit and WebPack
+-------------------------
+
+WebPack's support for WASM is still somewhat experimental, but PathKit can be
+used with a few configuration changes.
+
+In the JS code, use require():
+
+    const PathKitInit = require('experimental-pathkit-wasm/bin/pathkit.js')
+    PathKitInit().then((PathKit) => {
+        // Code goes here using PathKit
+    })
+
+Since WebPack does not expose the entire `/node_modules/` directory, but instead
+packages only the needed pieces, we have to copy pathkit.wasm into the build directory.
+One such solution is to use [CopyWebpackPlugin](https://github.com/webpack-contrib/copy-webpack-plugin)
+For example, add the following plugin:
+
+    config.plugins.push(
+        new CopyWebpackPlugin([
+            { from: 'node_modules/experimental-pathkit-wasm/bin/pathkit.wasm' }
+        ])
+    );
+
+If webpack gives an error similar to:
+
+    ERROR in ./node_modules/experimental-pathkit-wasm/bin/pathkit.js
+    Module not found: Error: Can't resolve 'fs' in '...'
+
+Then, add the following configuration change to the node section of the config:
+
+    config.node = {
+        fs: 'empty'
+    };
\ No newline at end of file
diff --git a/experimental/pathkit/npm-wasm/example.html b/experimental/pathkit/npm-wasm/example.html
new file mode 100644
index 0000000..d31e8b4
--- /dev/null
+++ b/experimental/pathkit/npm-wasm/example.html
@@ -0,0 +1,77 @@
+<!DOCTYPE html>
+<title>PathKit (Skia + WASM)</title>
+<meta charset="utf-8" />
+<meta http-equiv="X-UA-Compatible" content="IE=edge">
+<meta name="viewport" content="width=device-width, initial-scale=1.0">
+
+<style>
+  svg, canvas {
+    border: 1px dashed #AAA;
+  }
+
+  canvas {
+    width: 200px;
+    height: 200px;
+  }
+
+</style>
+
+<svg id=svg xmlns='http://www.w3.org/2000/svg' width=200 height=200></svg>
+
+<canvas id="canvas1"></canvas>
+
+<canvas id="canvas2"></canvas>
+
+<script type="text/javascript" src="/node_modules/experimental-pathkit-wasm/bin/pathkit.js"></script>
+
+<script type="text/javascript" charset="utf-8">
+
+  PathKitInit({
+    locateFile: (file) => '/node_modules/experimental-pathkit-wasm/bin/'+file,
+  }).then((PathKit) => {
+
+    let firstPath = PathKit.FromSVGString('M11.99 2C6.47 2 2 6.48 2 12s4.47 10 9.99 10C17.52 22 22 17.52 22 12S17.52 2 11.99 2zM12 20c-4.42 0-8-3.58-8-8s3.58-8 8-8 8 3.58 8 8-3.58 8-8 8zm.5-13H11v6l5.25 3.15.75-1.23-4.5-2.67z');
+
+    let secondPath = PathKit.NewPath();
+    // Acts somewhat like the Canvas API
+    secondPath.moveTo(1, 1);
+    secondPath.lineTo(20, 1);
+    secondPath.lineTo(10, 30);
+    secondPath.close();
+
+    let combinedPath = PathKit.ApplyPathOp(firstPath, secondPath, PathKit.PathOp.INTERSECT);
+    let simpleStr = PathKit.ToSVGString(combinedPath);
+
+    let newSVG = document.createElementNS('http://www.w3.org/2000/svg', 'path');
+    newSVG.setAttribute('stroke', 'rgb(0,0,200)');
+    newSVG.setAttribute('fill', 'white');
+    newSVG.setAttribute('transform', 'scale(5,5)');
+    newSVG.setAttribute('d', simpleStr);
+    document.getElementById('svg').appendChild(newSVG);
+
+    // Draw directly to Canvas
+    let ctx = document.getElementById('canvas1').getContext('2d');
+    ctx.strokeStyle = 'green';
+    ctx.fillStyle = 'white';
+    ctx.scale(8, 4);
+    ctx.beginPath();
+    PathKit.ToCanvas(combinedPath, ctx);
+    ctx.stroke();
+
+    // create Path2D object and use it in a Canvas.
+    let path2D = PathKit.ToPath2D(combinedPath);
+    ctx = document.getElementById('canvas2').getContext('2d');
+    ctx.scale(8, 4);
+    ctx.fillStyle = 'purple';
+    ctx.strokeStyle = 'orange';
+    ctx.fill(path2D);
+    ctx.stroke(path2D);
+
+    // clean up WASM memory
+    // See http://kripken.github.io/emscripten-site/docs/porting/connecting_cpp_and_javascript/embind.html?highlight=memory#memory-management
+    firstPath.delete();
+    secondPath.delete();
+    combinedPath.delete();
+  });
+
+</script>
diff --git a/experimental/pathkit/npm-wasm/package.json b/experimental/pathkit/npm-wasm/package.json
new file mode 100644
index 0000000..cb7fec1
--- /dev/null
+++ b/experimental/pathkit/npm-wasm/package.json
@@ -0,0 +1,11 @@
+{
+  "name": "experimental-pathkit-wasm",
+  "version": "0.0.4",
+  "description": "A WASM version of Skia's PathOps toolkit",
+  "main": "bin/pathkit.js",
+  "homepage": "https://github.com/google/skia/tree/master/experimental/pathkit",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "license": "Apache-2.0"
+}