Check java version in scripts running performance benchmarks.

Scripts throw exception if java version is not 1.8.*-internal

Bug:
Change-Id: I3c8487594ba15ef6b42433ba9bec2d22d5fa4a45
diff --git a/tools/run_proguard_dx_on_app.py b/tools/run_proguard_dx_on_app.py
index 8578d1e..92a75ba 100755
--- a/tools/run_proguard_dx_on_app.py
+++ b/tools/run_proguard_dx_on_app.py
@@ -56,6 +56,7 @@
   return parser.parse_args(argv)
 
 def Main(argv):
+  utils.check_java_version()
   options = parse_arguments(argv)
 
   outdir = options.out