Mojo: Add NotifyBadMessage API

mojo/edk/test/multiprocess_test_helper.h

Index: mojo/edk/test/multiprocess_test_helper.h
diff --git a/mojo/edk/test/multiprocess_test_helper.h b/mojo/edk/test/multiprocess_test_helper.h
index b3bed6b5bd4c0e7f0b151b69b5bb7f2cb03b05f9..5e3f5d5c1d44b93bbd91918227eed204dd3f36f0 100644
--- a/mojo/edk/test/multiprocess_test_helper.h
+++ b/mojo/edk/test/multiprocess_test_helper.h
@@ -42,6 +42,10 @@ class MultiprocessTestHelper {
       const std::string& switch_string,
       const std::string& switch_value);
 
+  void set_bad_message_callback(const base::Closure& callback) {
+    bad_message_callback_ = callback;
+  }
+
   // Wait for the child process to terminate.
   // Returns the exit code of the child process. Note that, though it's declared
   // to be an |int|, the exit code is subject to mangling by the OS. E.g., we
@@ -70,6 +74,8 @@ class MultiprocessTestHelper {
   // Valid after |StartChild()| and before |WaitForChildShutdown()|.
   base::Process test_child_;
 
+  base::Closure bad_message_callback_;
+
   DISALLOW_COPY_AND_ASSIGN(MultiprocessTestHelper);
 };