Use a custom Struct for stack trace storage

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index 9de1aebb01824fe53ad23ea7475bf7ec9e0fdca5..59054a71a20232222fb7f212025ae78fbb6f285f 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -1469,6 +1469,21 @@ class Isolate {
 #undef FIELD_ACCESSOR
 #undef THREAD_LOCAL_TOP_ACCESSOR
 
+// Constants for stack trace frames encoded into a fixed array.
+class EncodedStackTraceFrame : public AllStatic {
+ public:
+  static const int kWasmObjectOffset = 0;
+  static const int kWasmFunctionIndexOffset = 1;
+
+  static const int kReceiverOffset = 0;
+  static const int kFunctionOffset = 1;
+
+  static const int kCodeOffset = 2;
+  static const int kOffsetOffset = 3;
+  static const int kFlagsOffset = 4;
+
+  static const int kElementsPerFrame = 5;
+};
 
 class PromiseOnStack {
  public: