mojom: Add associative arrays to the mojom language.

mojo/public/cpp/bindings/lib/validation_errors.cc

Index: mojo/public/cpp/bindings/lib/validation_errors.cc
diff --git a/mojo/public/cpp/bindings/lib/validation_errors.cc b/mojo/public/cpp/bindings/lib/validation_errors.cc
index 0f55789161844c7bc0cadcc43e0f0e6b18835af0..b065d909de889ab1aa1d154cea4ec3f6706a3baf 100644
--- a/mojo/public/cpp/bindings/lib/validation_errors.cc
+++ b/mojo/public/cpp/bindings/lib/validation_errors.cc
@@ -40,6 +40,8 @@ const char* ValidationErrorToString(ValidationError error) {
       return "VALIDATION_ERROR_MESSAGE_HEADER_INVALID_FLAG_COMBINATION";
     case VALIDATION_ERROR_MESSAGE_HEADER_MISSING_REQUEST_ID:
       return "VALIDATION_ERROR_MESSAGE_HEADER_MISSING_REQUEST_ID";
+    case VALIDATION_ERROR_DIFFERENT_SIZED_ARRAYS_IN_MAP:
+      return "VALIDATION_ERROR_DIFFERENT_SIZED_ARRAYS_IN_MAP";
   }
 
   return "Unknown error";