DevTools: implement proxy server for hosted mode

third_party/WebKit/Source/devtools/hosted_mode/server.js

+// Copyright (c) 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+var fs = require("fs");
+var http = require("http");
+var path = require("path");
+var parseUrl = require("url").parse;
+
+var protocolFilesProxy = require("./protocol_files_proxy.js");
+
+var port = parseInt(process.env.PORT, 10) || 8090;
+
+http.createServer(requestHandler).listen(port);
+console.log("Starting hosted mode server at:\n  http://localhost:" + port);
+
+function requestHandler(request, response)
+{
+    var filePath = parseUrl(request.url).pathname;
+
+    if (filePath === "/front_end/InspectorBackendCommands.js") {
+        sendResponse(200, " ");
+        return;
+    }
+
+    if (protocolFilesProxy.proxy(filePath, sendResponse))
+        return;
+
+    var absoluteFilePath = path.join(process.cwd(), filePath);
+    fs.exists(absoluteFilePath, fsExistsCallback);
+
+    function fsExistsCallback(fileExists)
+    {
+        if (!fileExists) {
+            sendResponse(404, "404 - File not found");
+            return;
+        }
+        fs.readFile(absoluteFilePath, "binary", readFileCallback);
+    }
+
+    function readFileCallback(err, file)
+    {
+        if (err) {
+            sendResponse(500, `500 - Can't read file: ${err}`);
+            return;
+        }
+        sendResponse(200, file);
+    }
+
+    function sendResponse(statusCode, data)
+    {
+        response.writeHead(statusCode);
+        response.write(data, "binary");
+        response.end();
+    }
+}