Add the first app_shell_browsertest test.

apps/shell/browser/shell_browser_main_parts.h

Index: apps/shell/browser/shell_browser_main_parts.h
diff --git a/apps/shell/browser/shell_browser_main_parts.h b/apps/shell/browser/shell_browser_main_parts.h
index b29458413a8e1ea4f1a806929508886fbd8b6e43..f5082e1cbbdafeccec64f90ba803a2ff16443512 100644
--- a/apps/shell/browser/shell_browser_main_parts.h
+++ b/apps/shell/browser/shell_browser_main_parts.h
@@ -84,6 +84,10 @@ class ShellBrowserMainParts : public content::BrowserMainParts,
   // For running app browsertests.
   const content::MainFunctionParams parameters_;
 
+  // If true, indicates the main message loop should be run
+  // in MainMessageLoopRun. If false, it has already been run.
+  bool run_message_loop_;
+
   DISALLOW_COPY_AND_ASSIGN(ShellBrowserMainParts);
 };