[test] Common statusfile flag format for mozilla and test262.

Bug: v8:6917
Change-Id: Ida8594caead9119b7b5dad6209017e2eae9cd3aa
Reviewed-on: https://chromium-review.googlesource.com/776799
Commit-Queue: Michał Majewski <majeski@google.com>
Reviewed-by: Sergiy Byelozyorov <sergiyb@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49495}

test/mozilla/mozilla.status

@@ -938,7 +938,7 @@
 }], # 'arch == mipsel and simulator_run'
 
 ['arch == mips64el and simulator_run', {
-  'js1_5/extensions/regress-355497': [FAIL_OK, 'Flags: --sim-stack-size=512'],
+  'js1_5/extensions/regress-355497': [FAIL_OK, '--sim-stack-size=512'],
 }], # 'arch == mips64el and simulator_run'
 
 ['arch == mips', {
@@ -987,7 +987,7 @@
   'js1_5/extensions/regress-336410-1': [SKIP],
 
   #BUG(3152): Avoid C stack overflow.
-  'js1_5/extensions/regress-355497': [FAIL_OK, 'Flags: --sim-stack-size=512'],
+  'js1_5/extensions/regress-355497': [FAIL_OK, '--sim-stack-size=512'],
 }],  # 'arch == arm64 and simulator_run'
 
 ['variant == wasm_traps', {

tools/testrunner/local/testsuite.py

@@ -183,8 +183,8 @@ class TestSuite(object):
         if statusfile.DoSkip(t.outcomes):
           continue  # Don't add skipped tests to |filtered|.
         for outcome in t.outcomes:
-          if outcome.startswith('Flags: '):
-            t.flags += outcome[7:].split()
+          if outcome.startswith('--'):
+            t.flags += outcome.split()
         slow = statusfile.IsSlow(t.outcomes)
         pass_fail = statusfile.IsPassOrFail(t.outcomes)
       skip = False