Add support for assert statements with messages to the analyzer.

pkg/analyzer/test/generated/compile_time_error_code_test.dart

Index: pkg/analyzer/test/generated/compile_time_error_code_test.dart
diff --git a/pkg/analyzer/test/generated/compile_time_error_code_test.dart b/pkg/analyzer/test/generated/compile_time_error_code_test.dart
index 851a4ee69047ad753d280cbedd668fa751bf81b3..47857c8bd863c66befe9a05e9dd5fd587e30b026 100644
--- a/pkg/analyzer/test/generated/compile_time_error_code_test.dart
+++ b/pkg/analyzer/test/generated/compile_time_error_code_test.dart
@@ -262,6 +262,19 @@ main() {
     verify([source]);
   }
 
+  void test_assertWithExtraArgument() {
+    // TODO(paulberry): once DEP 37 is turned on by default, this test should
+    // be removed.
+    Source source = addSource('''
+f(bool x) {
+  assert(x, 'foo');
+}
+''');
+    computeLibrarySourceErrors(source);
+    assertErrors(source, [CompileTimeErrorCode.EXTRA_ARGUMENT_TO_ASSERT]);
+    verify([source]);
+  }
+
   void test_async_used_as_identifier_in_annotation() {
     Source source = addSource('''
 const int async = 0;