Run all message tests with a variant that forces preparsing

This will make sure that message tests cover both the parser and preparser
paths, just as we do for parsing-related cctests.

BUG=v8:4372
LOG=n

Review URL: https://codereview.chromium.org/1469383004

Cr-Commit-Position: refs/heads/master@{#32307}

test/message/testcfg.py

@@ -59,6 +59,10 @@ class MessageTestSuite(testsuite.TestSuite):
           tests.append(test)
     return tests
 
+  def CreateVariantGenerator(self, variants):
+    return super(MessageTestSuite, self).CreateVariantGenerator(
+        variants + ["preparser"])
+
   def GetFlagsForTestCase(self, testcase, context):
     source = self.GetSourceForTest(testcase)
     result = []

tools/testrunner/local/testsuite.py

@@ -44,6 +44,7 @@ ALL_VARIANT_FLAGS = {
   "ignition": [["--ignition", "--ignition-filter=*",
                 "--ignition-fake-try-catch",
                 "--ignition-fallback-on-eval-and-catch"]],
+  "preparser": [["--min-preparse-length=0"]],
 }
 
 # FAST_VARIANTS implies no --always-opt.
@@ -55,10 +56,11 @@ FAST_VARIANT_FLAGS = {
   "ignition": [["--ignition", "--ignition-filter=*",
                 "--ignition-fake-try-catch",
                 "--ignition-fallback-on-eval-and-catch"]],
+  "preparser": [["--min-preparse-length=0"]],
 }
 
 ALL_VARIANTS = set(["default", "stress", "turbofan", "turbofan_opt",
-                    "nocrankshaft", "ignition"])
+                    "nocrankshaft", "ignition", "preparser"])
 FAST_VARIANTS = set(["default", "turbofan"])
 STANDARD_VARIANT = set(["default"])