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..203eb117445b89381da8feb8317953b59ba0be07 100644
--- a/mojo/edk/test/multiprocess_test_helper.h
+++ b/mojo/edk/test/multiprocess_test_helper.h
@@ -12,6 +12,7 @@
 #include "base/process/process.h"
 #include "base/test/multiprocess_test.h"
 #include "base/test/test_timeouts.h"
+#include "mojo/edk/embedder/embedder.h"
 #include "mojo/public/cpp/system/message_pipe.h"
 #include "testing/multiprocess_func_list.h"
 
@@ -42,6 +43,10 @@ class MultiprocessTestHelper {
       const std::string& switch_string,
       const std::string& switch_value);
 
+  void set_process_error_callback(const ProcessErrorCallback& callback) {
+    process_error_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 +75,8 @@ class MultiprocessTestHelper {
   // Valid after |StartChild()| and before |WaitForChildShutdown()|.
   base::Process test_child_;
 
+  ProcessErrorCallback process_error_callback_;
+
   DISALLOW_COPY_AND_ASSIGN(MultiprocessTestHelper);
 };