[wasm][asm.js] Fix and enable several asm.js tests with the new parser.

src/wasm/wasm-module-builder.cc

Index: src/wasm/wasm-module-builder.cc
diff --git a/src/wasm/wasm-module-builder.cc b/src/wasm/wasm-module-builder.cc
index b1b859ba42cbd9c0d63b2c0950869760a7f8b42b..73f68e891f6b5a5c457b10ff97cbe92340dd7b11 100644
--- a/src/wasm/wasm-module-builder.cc
+++ b/src/wasm/wasm-module-builder.cc
@@ -190,9 +190,10 @@ void WasmFunctionBuilder::StashCode(std::vector<byte>* dst, size_t position) {
     body_.resize(position);
     return;
   }
+  DCHECK_LE(position, body_.size());
   size_t len = body_.size() - position;
   dst->resize(len);
-  memcpy(dst->data(), &body_[position], len);
+  memcpy(dst->data(), body_.data() + position, len);
   body_.resize(position);
 }