[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..5184b3dd8f573507d173a3b9f648355b8119eefe 100644
--- a/src/wasm/wasm-module-builder.cc
+++ b/src/wasm/wasm-module-builder.cc
@@ -190,7 +190,12 @@ 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;
+  if (len == 0) {
+    // Early out here as body_[position] is out of bounds in this case.

[Clemens Hammacher, 2017/03/28 09:52:02]

dst->resize(0) is not needed here?

You can avoid this special case for len == 0 by changing "&body_[position]" to
"body_.data() + position".

[bradnelson, 2017/03/28 15:30:50]

Ah good point.
Done.

+    return;
+  }
   dst->resize(len);
   memcpy(dst->data(), &body_[position], len);
   body_.resize(position);