Encode interpreter::SourcePositionTable as variable-length ints.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index b46d0ec318cee88fa820fa3be4b440470fbecd41..f4b816184cf7b1e26ff8ab7110665ee502be9d3e 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -3031,7 +3031,7 @@ AllocationResult Heap::AllocateBytecodeArray(int length,
   instance->set_parameter_count(parameter_count);
   instance->set_constant_pool(constant_pool);
   instance->set_handler_table(empty_fixed_array());
-  instance->set_source_position_table(empty_fixed_array());
+  instance->set_source_position_table(empty_byte_array());
   CopyBytes(instance->GetFirstBytecodeAddress(), raw_bytecodes, length);
 
   return result;