[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..548c2d0b672ed8581e4e0d0b0795e52fe0406d0f 100644
--- a/src/wasm/wasm-module-builder.cc
+++ b/src/wasm/wasm-module-builder.cc
@@ -191,6 +191,10 @@ void WasmFunctionBuilder::StashCode(std::vector<byte>* dst, size_t position) {
     return;
   }
   size_t len = body_.size() - position;
+  if (len == 0) {
+    // TODO(bradnelson): Figure out why the memcpy crashes if len == 0.

[Michael Starzinger, 2017/03/24 11:56:05]

It is not the memcpy that crashes but the accessor to body_[position] if
position == body_.size(). This is an out-of-bounds access. I think the early
return is the best fix for this case.

On a related note, what about the case where position > body_.size()? Do we care
about this case? Could we add a DCHECK_LE(position, body_.size()) into this
method?

[bradnelson, 2017/03/28 04:34:31]

Done.

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