Some changes to performance test script.

tools/testing/browser_README.txt

 Overview:
  These are the instructions to run a wide variety of browser tests using 
  test.dart --component=webdriver or 
  dart/tools/testing/perf_testing/create_graph.py. Currently the results of
  create_graph are uploaded to https://dartperf.googleplex.com/. 
  
 ============== Windows Setup ==============
 
 Open Internet Explorer. Open the Internet Options dialog, and move to the
 "Security" tab. Click through Internet, Local Intranet, Trusted sites, and
@@ skipping 56 matching lines @@
 ========= Proceed further only if you also want to run performance tests.======
 
 10)Download appengine for Python and place it in third_party (http://code.google.com/appengine/downloads.html#Google_App_Engine_SDK_for_Python):
   "dart/third_party/appengine-python/"
 
 11)Install matplotlib http://matplotlib.sourceforge.net/
 
 12)Pull down benchmarks from internal repo (Google only): 
    http://chromegw.corp.google.com/viewvc/dash/trunk/internal/browserBenchmarks/README.txt?view=markup
 
-13)TODO(efortuna): Deal with appengine check in! Run 
-   '../../../third_party/appengine-python/1.5.4/appcfg.py update appengine/' 
-   while standing in dart/tools/testing/perf_tests.
+13)Create a directory in called appengine-python in third_party. Download and 
+   install App Engine in the directory you just created. 
+   http://code.google.com/appengine/downloads.html
 
 14) Run the tests! While standing in dart/tools/testing/perf_testing, run 
     $> python create_graph.py --forever --verbose 
     to run all the tests (browser performance, language correctness in the
     browser, command line performance, and self-hosted compile time and compiled
     code size). 
     
     You can run individual tests by adding the particular option (such as 
     --language) when running create_graph.py. Type "create_graph.py -h" for a 
     full list of the options.