[wasm] Initial signal handler

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index b76d3357a32e9f4c2fc3750895f75471d3fd5909..39fafcd21ec1ae1ac16c71f0dcaf64a02f5083df 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -5132,6 +5132,10 @@ class Code: public HeapObject {
   // corresponding landing pad offsets.
   DECL_ACCESSORS(protected_instructions, FixedArray)
 
+  // [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.
@@ -5524,7 +5528,8 @@ 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 + kIntSize;
 
   enum TrapFields { kTrapCodeOffset, kTrapLandingOffset, kTrapDataSize };