Handle co19 @dynamic-type-error better.

dart/tests/co19/testcfg.py

Index: dart/tests/co19/testcfg.py
diff --git a/dart/tests/co19/testcfg.py b/dart/tests/co19/testcfg.py
index f4250b9216aa0caffd8d877b07c0f5ba5b9f0d64..2732bb62ee0336a2cf68e2d6b5f6714f9a13efd9 100644
--- a/dart/tests/co19/testcfg.py
+++ b/dart/tests/co19/testcfg.py
@@ -27,15 +27,12 @@ class Co19TestCase(test.TestCase):
   def IsNegative(self):
     if self._is_negative is None :
       contents = self.GetSource()
-      for tag in ('@compile-error',
-                  # '@static-type-error',
-                  '@dynamic-type-error', '@runtime-error'):
-        if tag in contents:
-          self._is_negative = True
-          break
-      else :
+      if '@compile-error' in contents or '@runtime-error' in contents:
+        self._is_negative = True
+      elif '@dynamic-type-error' in contents:
+        self._is_negative = self.context.checked
+      else:
         self._is_negative = False
-
     return self._is_negative
 
   def GetLabel(self):