Reduce flakiness in chrome_frame_tests.exe by having each run in a clean environment.

chrome_frame/test/test_scrubber.h

Index: chrome_frame/test/test_scrubber.h
diff --git a/chrome_frame/test/test_scrubber.h b/chrome_frame/test/test_scrubber.h
new file mode 100644
index 0000000000000000000000000000000000000000..fa4d79a6d3b704ebfc318e0ba64e8f03de216b39
--- /dev/null
+++ b/chrome_frame/test/test_scrubber.h
@@ -0,0 +1,33 @@
+// Copyright (c) 2012 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.
+
+// The TestScrubber cleans up machine state between tests. This includes killing

[robertshield, 2012/02/27 21:13:42]

The TestScrubber class isn't exposed to callers, from the looks of things it's
more an implementation detail of the utility functions below. Feels like this
comment belongs in the .cc file, with an expanded comment on the
InstallTestScrubber function below. 

[grt (UTC plus 2), 2012/02/28 03:12:04]

I changed "TestScrubber" to "test scrubber".  Otherwise, I think the comment is
good since it says what the scrubber does (cleans up state) and how it must be
set in motion (you gots ta call the Install func), not how it does it (a Google
test listener).

+// all Internet Explorer processes, killing all Chrome processes spawned by
+// Chrome Frame, and deleting the user data directory.  The scrubber must be
+// installed before tests are run via |InstallTestScrubber|.
+//
+// Tests that use a non-standard user data directory must provide that directory
+// to the scrubber via |OverrideDataDirectoryForThisTest()|.
+
+#ifndef CHROME_FRAME_TEST_TEST_SCRUBBER_H_
+#define CHROME_FRAME_TEST_TEST_SCRUBBER_H_
+#pragma once
+
+#include "base/string_piece.h"

[robertshield, 2012/02/27 21:13:42]

I think you could forward declare StringPiece16 as well if you wanted to. 

[grt (UTC plus 2), 2012/02/28 03:12:04]

I think that'd involve several forward decls since StringPiece16 is a typedef of
BasicStringPiece, so I'll pass.

+
+namespace testing {
+class UnitTest;
+}
+
+namespace chrome_frame_test {
+
+// Install the scrubber in |unit_test| (call before RUN_ALL_TESTS).
+void InstallTestScrubber(testing::UnitTest* unit_test);
+
+// Override the user data directory for the current test.

[robertshield, 2012/02/27 21:13:42]

I might be misreading the implementation, but it feels like all this method does
is set a path to be deleted when the test completes.

[grt (UTC plus 2), 2012/02/28 03:12:04]

Comments updated (here and at the top of the file).

+void OverrideDataDirectoryForThisTest(const base::StringPiece16& user_data_dir);
+
+}  // namespace chrome_frame_test
+
+#endif  // CHROME_FRAME_TEST_TEST_SCRUBBER_H_