Introduce new interception API (#242)

This patch introduces new interception API, via killing InterceptedRequest and giving the `abort` and `continue` methods to the Request object.

lib/Multimap.js

@@ -0,0 +1,138 @@
+/**
+ * Copyright 2017 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * 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
+ * limitations under the License.
+ */
+
+/**
+ * @template K, V
+ */
+class Multimap {
+  constructor() {
+    /** @type {!Map<K, !Set<!V>>} */
+    this._map = new Map();
+  }
+
+  /**
+   * @param {K} key
+   * @param {V} value
+   */
+  set(key, value) {
+    let set = this._map.get(key);
+    if (!set) {
+      set = new Set();
+      this._map.set(key, set);
+    }
+    set.add(value);
+  }
+
+  /**
+   * @param {K} key
+   * @return {!Set<!V>}
+   */
+  get(key) {
+    let result = this._map.get(key);
+    if (!result)
+      result = new Set();
+    return result;
+  }
+
+  /**
+   * @param {K} key
+   * @return {boolean}
+   */
+  has(key) {
+    return this._map.has(key);
+  }
+
+  /**
+   * @param {K} key
+   * @param {V} value
+   * @return {boolean}
+   */
+  hasValue(key, value) {
+    let set = this._map.get(key);
+    if (!set)
+      return false;
+    return set.has(value);
+  }
+
+  /**
+   * @return {number}
+   */
+  get size() {
+    return this._map.size;
+  }
+
+  /**
+   * @param {K} key
+   * @param {V} value
+   * @return {boolean}
+   */
+  delete(key, value) {
+    let values = this.get(key);
+    let result = values.delete(value);
+    if (!values.size)
+      this._map.delete(key);
+    return result;
+  }
+
+  /**
+   * @param {K} key
+   */
+  deleteAll(key) {
+    this._map.delete(key);
+  }
+
+  /**
+   * @return {!Array<K>}
+   */
+  keysArray() {
+    return this._map.keysArray();
+  }
+
+  /**
+   * @param {K} key
+   * @return {?V} value
+   */
+  firstValue(key) {
+    let set = this._map.get(key);
+    if (!set)
+      return null;
+    return set.values().next().value;
+  }
+
+  /**
+   * @return {K}
+   */
+  firstKey() {
+    return this._map.keys().next().value;
+  }
+
+  /**
+   * @return {!Array<!V>}
+   */
+  valuesArray() {
+    let result = [];
+    let keys = this.keysArray();
+    for (let i = 0; i < keys.length; ++i)
+      result.pushAll(this.get(keys[i]).valuesArray());
+    return result;
+  }
+
+  clear() {
+    this._map.clear();
+  }
+}
+
+module.exports = Multimap;