[doclint] Move doclint under utils/

This patch:
- moves doclint under utils/ folder
- adds tests to verify doclint basic functionality

This patch also drops the jasmine as a spec runner for the doclint
checks. It turned out it's hard to customize jasmine's behavior,
so instead this patch implements a dummy spec runner.

The dummy spec runner allows us:
- to format messages however we want (the custom jasmine reporter would
  also allow us to do this)
- to avoid `beforeAll` functions which pollute global to pass
  initialized variables over to specs

References #14

utils/doclint/JSBuilder.js

@@ -0,0 +1,93 @@
+const fs = require('fs');
+const path = require('path');
+const esprima = require('esprima');
+const ESTreeWalker = require('../../third_party/chromium/ESTreeWalker');
+const Documentation = require('./Documentation');
+
+class JSOutline {
+  constructor(text) {
+    this.classes = [];
+    this._currentClassName = null;
+    this._currentClassMethods = [];
+    this._currentClassProperties = [];
+
+    this._text = text;
+    let ast = esprima.parseScript(this._text, {loc: true, range: true});
+    let walker = new ESTreeWalker(node => {
+      if (node.type === 'ClassDeclaration')
+        this._onClassDeclaration(node);
+      else if (node.type === 'MethodDefinition')
+        this._onMethodDefinition(node);
+    });
+    walker.walk(ast);
+    this._flushClassIfNeeded();
+  }
+
+  _onClassDeclaration(node) {
+    this._flushClassIfNeeded();
+    this._currentClassName = this._extractText(node.id);
+  }
+
+  _onMethodDefinition(node) {
+    console.assert(this._currentClassName !== null);
+    console.assert(node.value.type === 'FunctionExpression');
+    const args = [];
+    for (let param of node.value.params)
+      args.push(new Documentation.Argument(this._extractText(param)));
+    let methodName = this._extractText(node.key);
+    let method = new Documentation.Method(methodName, args);
+    this._currentClassMethods.push(method);
+    // Extract properties from constructor.
+    if (node.kind === 'constructor') {
+      let walker = new ESTreeWalker(node => {
+        if (node.type !== 'AssignmentExpression')
+          return;
+        node = node.left;
+        if (node.type === 'MemberExpression' && node.object &&
+            node.object.type === 'ThisExpression' && node.property &&
+            node.property.type === 'Identifier')
+          this._currentClassProperties.push(node.property.name);
+      });
+      walker.walk(node);
+    }
+    return ESTreeWalker.SkipSubtree;
+  }
+
+  _onMemberExpression(node) {
+
+  }
+
+  _flushClassIfNeeded() {
+    if (this._currentClassName === null)
+      return;
+    let jsClass = new Documentation.Class(this._currentClassName, this._currentClassMethods, this._currentClassProperties);
+    this.classes.push(jsClass);
+    this._currentClassName = null;
+    this._currentClassMethods = [];
+    this._currentClassProperties = [];
+  }
+
+  _extractText(node) {
+    if (!node)
+      return null;
+    let text = this._text.substring(node.range[0], node.range[1]).trim();
+    return text;
+  }
+}
+
+/**
+ * @param {!Array<string>} dirPath
+ * @return {!Promise<!Documentation>}
+ */
+module.exports = async function(dirPath) {
+  let filePaths = fs.readdirSync(dirPath)
+      .filter(fileName => fileName.endsWith('.js'))
+      .map(fileName => path.join(dirPath, fileName));
+  let classes = [];
+  for (let filePath of filePaths) {
+    let outline = new JSOutline(fs.readFileSync(filePath, 'utf8'));
+    classes.push(...outline.classes);
+  }
+  return new Documentation(classes);
+};
+