[Mac] Add interactive App Shim test.

chrome/browser/web_applications/web_app_mac.mm

Index: chrome/browser/web_applications/web_app_mac.mm
diff --git a/chrome/browser/web_applications/web_app_mac.mm b/chrome/browser/web_applications/web_app_mac.mm
index 3a7b237f1f4e34fa21c738e9af121cd5470ece5f..64575f067802ffde1fa2c99d886c16ea1496033d 100644
--- a/chrome/browser/web_applications/web_app_mac.mm
+++ b/chrome/browser/web_applications/web_app_mac.mm
@@ -44,6 +44,8 @@
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/image/image_family.h"
 
+bool g_app_shims_enable_internal_for_test = false;
+
 namespace {
 
 // Launch Services Key to run as an agent app, which doesn't launch in the dock.
@@ -854,7 +856,7 @@ base::FilePath GetAppInstallPath(const ShortcutInfo& shortcut_info) {
 }
 
 void MaybeLaunchShortcut(const ShortcutInfo& shortcut_info) {
-  if (AppShimsDisabledForTest())
+  if (AppShimsDisabledForTest() && !g_app_shims_enable_internal_for_test)
     return;
 
   content::BrowserThread::PostTask(
@@ -946,7 +948,7 @@ void UpdatePlatformShortcuts(
     const ShortcutInfo& shortcut_info,
     const extensions::FileHandlersInfo& file_handlers_info) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::FILE));
-  if (AppShimsDisabledForTest())
+  if (AppShimsDisabledForTest() && !g_app_shims_enable_internal_for_test)
     return;
 
   WebAppShortcutCreator shortcut_creator(