[wasm] Provide better stack traces for asm.js code

src/wasm/decoder.h

Index: src/wasm/decoder.h
diff --git a/src/wasm/decoder.h b/src/wasm/decoder.h
index b556f932badd25f22215950ed8784568e76731b3..8c126c5546d5f94b63a20751ea2af90aed92fd08 100644
--- a/src/wasm/decoder.h
+++ b/src/wasm/decoder.h
@@ -279,8 +279,8 @@ class Decoder {
     error_msg_.reset();
   }
 
-  bool ok() const { return error_pc_ == nullptr; }
-  bool failed() const { return !!error_msg_; }
+  bool ok() const { return error_msg_ == nullptr; }
+  bool failed() const { return !ok(); }
   bool more() const { return pc_ < limit_; }
 
   const byte* start() { return start_; }