[Mac] Add interactive App Shim test.

apps/app_shim/chrome_main_app_mode_mac.mm

 // Copyright 2013 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.
 
 // On Mac, one can't make shortcuts with command-line arguments. Instead, we
 // produce small app bundles which locate the Chromium framework and load it,
 // passing the appropriate data. This is the entry point into the framework for
 // those app bundles.
 
 #import <Cocoa/Cocoa.h>
@@ skipping 593 matching lines @@
         runningApplicationsWithBundleIdentifier:chrome_bundle_id];
     if ([existing_chrome count] > 0)
       pid = [[existing_chrome objectAtIndex:0] processIdentifier];
   }
 
   AppShimController controller;
   base::MessageLoopForUI main_message_loop;
   main_message_loop.set_thread_name("MainThread");
   base::PlatformThread::SetName("CrAppShimMain");
 
-  if (pid == -1) {
+  // In tests, launching Chrome does nothing, and we won't get a ping response,
+  // so just assume the socket exists.
+  if (pid == -1 &&
+      !CommandLine::ForCurrentProcess()->HasSwitch(
+          app_mode::kLaunchedForTest)) {
     // Launch Chrome if it isn't already running.
     ProcessSerialNumber psn;
     CommandLine command_line(CommandLine::NO_PROGRAM);
     command_line.AppendSwitch(switches::kSilentLaunch);
 
     // If the shim is the app launcher, pass --show-app-list when starting a new
     // Chrome process to inform startup codepaths and load the correct profile.
     if (info->app_mode_id == app_mode::kAppListModeId) {
       command_line.AppendSwitch(switches::kShowAppList);
     } else {
@@ skipping 31 matching lines @@
     // minute.
     main_message_loop.PostTask(
         FROM_HERE,
         base::Bind(&AppShimController::Init,
                    base::Unretained(&controller)));
   }
 
   main_message_loop.Run();
   return 0;
 }