Bug 1356652 - Add a README_MOZILLA file to the Speedometer directory; r=Ehsan,ted

MozReview-Commit-ID: 6mUMxcO0zzH

--HG--
extra : rebase_source : 71abeed10abbee28e30882c6cc2bc6c2125daaf0

third_party/speedometer/README_MOZILLA

@@ -0,0 +1,13 @@
+The source from this directory was copied from the
+PerformanceTests/Speedometer directory of the Webkit repository
+at: https://svn.webkit.org/repository/webkit/trunk
+
+The SVN revision used was: 221009
+
+The contents of this directory are intended for use to "train" the
+profile guided optimization (PGO) of Firefox and for benchmarking
+scenarios. The files inside this directory are not intended to ship
+with Firefox or any other product. If files inside this directory
+are useful for other purposes (e.g. JavaScript libraries), consumers
+should vendor those files separately, as it is not appropriate to pull
+in components of Speedometer for use outside of Speedometer.