Add test driver with the notion of perf tests.

BUG=374740
LOG=n
R=dslomov@chromium.org

Review URL: https://codereview.chromium.org/526953005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23569 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

benchmarks/v8.json

@@ -3,7 +3,7 @@
   "main": "run.js",
   "run_count": 2,
   "results_regexp": "^%s: (.+)$",
-  "benchmarks": [
+  "tests": [
     {"name": "Richards"},
     {"name": "DeltaBlue"},
     {"name": "Crypto"},