Fix windows performance tests.

tools/testing/perf_testing/create_graph.py

Index: tools/testing/perf_testing/create_graph.py
===================================================================
--- tools/testing/perf_testing/create_graph.py	(revision 3854)
+++ tools/testing/perf_testing/create_graph.py	(working copy)
@@ -92,6 +92,10 @@
   run_cmd(['svn', 'revert',  os.path.join(os.getcwd(), 'frog', 'minfrog')])
 
   run_cmd(['gclient', 'sync'])
+  
+  def on_rm_error(func, path, exc_info):

[Emily Fortuna, 2012/02/02 18:24:09]

On windows, the output directory is marked as "Read only" for some reason, so we
get an error when we try to delete it simply using shutil.rmtree.

[Siggi Cherem (dart-lang), 2012/02/02 18:29:58]

It would be great to put this exact comment on the code :)

[Emily Fortuna, 2012/02/02 18:51:00]

Done.

+    os.chmod(path, stat.S_IWRITE)
+    os.unlink(path)
   # TODO(efortuna): building the sdk locally is a band-aid until all build
   # platform SDKs are hosted in Google storage. Pull from https://sandbox.
   # google.com/storage/?arg=dart-dump-render-tree#dart-dump-render-tree%2Fsdk
@@ -100,7 +104,7 @@
   # have test statistics for what's passing on x64. Eliminate arch specification
   # when we have tests running on x64, too.
   shutil.rmtree(os.path.join(os.getcwd(), 
-    utils.GetBuildRoot(utils.GuessOS(), 'release', 'ia32')))
+    utils.GetBuildRoot(utils.GuessOS(), 'release', 'ia32')), onerror=on_rm_error)
   lines = run_cmd([os.path.join('.', 'tools', 'build.py'), '-m', 'release',
     '--arch=ia32', 'create_sdk'])