[wasm] Initial signal handler

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 0bbb3955da2ef032fb0bae54c7546e01fb41a45f..15651c1db279cc2e7f2484ad89a73714191ae668 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -4915,6 +4915,10 @@ class Code: public HeapObject {
   // [source_position_table]: ByteArray for the source positions table.
   DECL_ACCESSORS(source_position_table, ByteArray)
 
+  // [trap_handler_index]: An index into the trap handler's master list of code
+  // objects.
+  DECL_ACCESSORS(trap_handler_index, Smi)
+
   // [raw_type_feedback_info]: This field stores various things, depending on
   // the kind of the code object.
   //   FUNCTION           => type feedback information.
@@ -5303,7 +5307,8 @@ class Code: public HeapObject {
   static const int kConstantPoolOffset = kPrologueOffset + kIntSize;
   static const int kBuiltinIndexOffset =
       kConstantPoolOffset + kConstantPoolSize;
-  static const int kHeaderPaddingStart = kBuiltinIndexOffset + kIntSize;
+  static const int kTrapHandlerIndex = kBuiltinIndexOffset + kIntSize;
+  static const int kHeaderPaddingStart = kTrapHandlerIndex + kPointerSize;
 
   enum TrapFields { kTrapCodeOffset, kTrapLandingOffset, kTrapDataSize };