Add a ExtensionBrowserTest base class

chrome/test/in_process_browser_test.h

Index: chrome/test/in_process_browser_test.h
diff --git a/chrome/test/in_process_browser_test.h b/chrome/test/in_process_browser_test.h
index 27f5bff750a43b422b39bddc7e870287aab0b6bb..64bf1ea3fd4056404cc1b7c6cbacbe6f303ac6b1 100644
--- a/chrome/test/in_process_browser_test.h
+++ b/chrome/test/in_process_browser_test.h
@@ -62,6 +62,10 @@ class InProcessBrowserTest : public testing::Test {
   // Override this to add command line flags specific to your test.
   virtual void SetUpCommandLine(CommandLine* command_line) {}
 
+  // Override this to add any custom cleanup code that needs to be done on the
+  // main thread before the browser is torn down.
+  virtual void CleanUpOnMainThread() {}
+
   // Allows subclasses to configure the host mapper. By default this blocks
   // requests to google.com as Chrome pings that on startup and we don't want to
   // do that during testing.