Instrument serial API code to make testing easier.

chrome/test/data/extensions/api_test/serial/api/background.js

 // Copyright (c) 2012 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.
 
 // TODO(miket): opening Bluetooth ports on OSX is unreliable. Investigate.
 function shouldSkipPort(portName) {
   return portName.match(/[Bb]luetooth/);
 }
 
 var testGetPorts = function() {
@@ skipping 119 matching lines @@
       while (portNumber < ports.length) {
         if (shouldSkipPort(ports[portNumber])) {
           portNumber++;
           continue;
         } else
           break;
       }
       if (portNumber < ports.length) {
         serialPort = ports[portNumber];
         var bitrate = 57600;
-        console.log('Connecting to serial device ' + serialPort + ' at ' +
+        console.log('Opening serial device ' + serialPort + ' at ' +
                     bitrate + ' bps.');
         chrome.experimental.serial.open(serialPort, {bitrate: bitrate},
                                         onOpen);
       } else {
         // We didn't find a port that we think we should try.
         chrome.test.succeed();
       }
     } else {
       // No serial device found. This is still considered a success because we
       // can't rely on specific hardware being present on the machine.
       chrome.test.succeed();
     }
   };
 
   chrome.experimental.serial.getPorts(onGetPorts);
 };
 
-var onMessageReply = function(message) {
-  var tests = [testGetPorts, testMaybeOpenPort];
-
-  // Another way to force the test to run.
-  var runTest = false;
-
-  if (runTest || message == 'echo_device_attached') {
-    // We have a specific serial port set up to respond to test traffic. This
-    // is a rare situation. TODO(miket): mock to make it testable under any
-    // hardware conditions.
-    tests.push(testSerial);
-  }
-  chrome.test.runTests(tests);
-};
-
-chrome.test.sendMessage('serial_port', onMessageReply);
+var tests = [testGetPorts, testMaybeOpenPort, testSerial];
+chrome.test.runTests(tests);