Whitelist serialized objects wrt MSAN.

src/serialize.cc

Index: src/serialize.cc
diff --git a/src/serialize.cc b/src/serialize.cc
index 887276f9cf0dc1b65e6f90432e14cea0b205e9e3..b7277b5da563927fcd755ab97f7104feca1106e0 100644
--- a/src/serialize.cc
+++ b/src/serialize.cc
@@ -2120,6 +2120,10 @@ int Serializer::ObjectSerializer::OutputRawData(
     }
 
     const char* description = code_object_ ? "Code" : "Byte";
+#ifdef MEMORY_SANITIZER
+    // Object sizes are usually rounded up with uninitialized padding space.
+    MSAN_MEMORY_IS_INITIALIZED(object_start + base, bytes_to_output);
+#endif  // MEMORY_SANITIZER
     sink_->PutRaw(object_start + base, bytes_to_output, description);
     if (code_object_) delete[] object_start;
   }