refactor: move Connection to use ConnectionTransport (#3217)

Currently connection assumes that transport is a websocket
and tries to handle websocket-related errors.

This patch:
- moves ConnectionTransport interface to use callbacks instead
  of events. This way it could be used in browser context as well.
- introduces WebSocketTransport that implements ConnectionTransport
  interface for ws.

This is a preparation step for 2 things:
- exposing `transport` option in the `puppeteer.connect` method
- better support for `browserify`

References #2119

lib/PipeTransport.js

@@ -0,0 +1,74 @@
+/**
+ * Copyright 2018 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.
+ */
+const {helper} = require('./helper');
+
+/**
+ * @implements {!Puppeteer.ConnectionTransport}
+ */
+class PipeTransport {
+  /**
+   * @param {!NodeJS.WritableStream} pipeWrite
+   * @param {!NodeJS.ReadableStream} pipeRead
+   */
+  constructor(pipeWrite, pipeRead) {
+    this._pipeWrite = pipeWrite;
+    this._pendingMessage = '';
+    this._eventListeners = [
+      helper.addEventListener(pipeRead, 'data', buffer => this._dispatch(buffer))
+    ];
+    this.onmessage = null;
+    this.onclose = null;
+  }
+
+  /**
+   * @param {string} message
+   */
+  send(message) {
+    this._pipeWrite.write(message);
+    this._pipeWrite.write('\0');
+  }
+
+  /**
+   * @param {!Buffer} buffer
+   */
+  _dispatch(buffer) {
+    let end = buffer.indexOf('\0');
+    if (end === -1) {
+      this._pendingMessage += buffer.toString();
+      return;
+    }
+    const message = this._pendingMessage + buffer.toString(undefined, 0, end);
+    if (this.onmessage)
+      this.onmessage.call(null, message);
+
+    let start = end + 1;
+    end = buffer.indexOf('\0', start);
+    while (end !== -1) {
+      if (this.onmessage)
+        this.onmessage.call(null, buffer.toString(undefined, start, end));
+      start = end + 1;
+      end = buffer.indexOf('\0', start);
+    }
+    this._pendingMessage = buffer.toString(undefined, start);
+  }
+
+  close() {
+    this._pipeWrite = null;
+    helper.removeEventListeners(this._eventListeners);
+  }
+}
+
+module.exports = PipeTransport;