Start app shim when app launched.

apps/app_shim/app_shim_util_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.
+
+#include "apps/app_shim/app_shim_util.h"
+
+#include "apps/app_shim/switches.h"
+#include "base/command_line.h"
+#include "base/file_util.h"
+#include "base/files/file_path.h"
+#include "base/mac/foundation_util.h"
+#include "base/mac/launch_services_util.h"
+#include "base/strings/sys_string_conversions.h"
+#include "chrome/common/mac/app_mode_common.h"
+#include "content/public/browser/browser_thread.h"
+
+using content::BrowserThread;
+
+namespace {
+
+const char kAppDirName[] = "Chrome Apps.localized";

[tapted, 2013/05/16 04:51:00]

maybe now is a good time to discuss with benwells whether this should be split
into 

Chromium Apps
Chrome Canary Apps
Chrome Apps

+
+base::FilePath GetWritableApplicationsDirectory() {
+  base::FilePath path;
+  if (base::mac::GetLocalDirectory(NSApplicationDirectory, &path) &&
+      file_util::PathIsWritable(path)) {
+    return path;
+  }
+  if (base::mac::GetUserDirectory(NSApplicationDirectory, &path))
+    return path;
+  return base::FilePath();
+}
+
+base::FilePath GetPathToShim(const std::string& app_id,

[tapted, 2013/05/16 04:51:00]

Maybe we should consider calling this extension_id. On balance, I think it's
more consistent with the non-mac code, but I realise the app_shim_host uses
app_id (but there it's doing double duty as a "appmode" id in the OS sense).
So... when it's not ambiguous I'd say go with extension_id ;)

+                             const std::string& profile_name) {
+  base::FilePath app_dir = app_shim::GetAppShimFolder();
+  if (app_dir.empty())
+    return base::FilePath();
+
+  file_util::FileEnumerator enumerator(app_dir,

[tapted, 2013/05/16 04:51:00]

perhaps a note to say why it's iterating (i.e. because extension may have been
updated with a new name, so a search must be done to look for a matching
extension id).

+                                       false /* recursive */,
+                                       file_util::FileEnumerator::DIRECTORIES);
+  base::FilePath shim_path = enumerator.Next();
+  for (; !shim_path.empty(); shim_path = enumerator.Next()) {
+    base::FilePath plist_path =
+        shim_path.Append("Contents").Append("Info.plist");
+    NSDictionary* plist = [NSDictionary dictionaryWithContentsOfFile:
+        base::mac::FilePathToNSString(plist_path)];
+    std::string plist_id = base::SysNSStringToUTF8(
+        [plist objectForKey:app_mode::kCrAppModeShortcutIDKey]);
+    std::string plist_profile = base::SysNSStringToUTF8(
+        [plist objectForKey:app_mode::kCrAppModeProfileDirKey]);
+
+    if (plist_id == app_id && plist_profile == profile_name) {
+      break;
+    }

[tapted, 2013/05/16 04:51:00]

nit: doesn't need curlies

+  }
+  return shim_path;
+}
+
+void FindAndLaunchShimOnFileThread(
+    const std::string& app_id,

[tapted, 2013/05/16 04:51:00]

nit: align these with the open paren (like for FindAndLaunchShimForApp in the
header)

+    const std::string& profile_name,
+    base::Callback<void(bool)> completed) {
+  base::FilePath shim_path = GetPathToShim(app_id, profile_name);

[tapted, 2013/05/16 04:51:00]

nit: before this, 
  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::FILE));

+  if (shim_path.empty()) {
+    BrowserThread::PostTask(
+        BrowserThread::UI, FROM_HERE, base::Bind(completed, false));
+    return;
+  }

[tapted, 2013/05/16 04:51:00]

nit: blank line after for early return

+  CommandLine command_line(CommandLine::NO_PROGRAM);
+  command_line.AppendSwitch(app_shim::switches::kNoLaunchApp);
+  base::mac::OpenApplicationWithPath(shim_path, command_line, NULL);

[tapted, 2013/05/16 04:51:00]

Do you see a reason why shim_path can't be derived from 

base::FilePath CommandLine::GetProgram() instead?

clearly OpenApplicationWithPath would need an update too. Maybe that can be
addressed along with the TODO "this opens a new broser window.."

+  BrowserThread::PostTask(
+      BrowserThread::UI, FROM_HERE, base::Bind(completed, true));
+}
+
+}  // namespace
+
+namespace app_shim {
+
+base::FilePath GetAppShimFolder() {
+  base::FilePath path = GetWritableApplicationsDirectory();

[tapted, 2013/05/16 04:51:00]

GetWritableApplicationsDirectory might need to be called on the FILE thread

+  return path.empty() ? path : path.Append(kAppDirName);
+}
+
+void FindAndLaunchShimForApp(
+    const std::string& app_id,

[tapted, 2013/05/16 04:51:00]

nit: align these like the header

+    const std::string& profile_name,
+    base::Callback<void(bool)> completed) {
+  BrowserThread::PostTask(
+      BrowserThread::FILE, FROM_HERE,
+      base::Bind(&FindAndLaunchShimOnFileThread,
+          app_id, profile_name, completed));
+}
+
+}  // namespace app_shim