Consolidate WASM bindings into a single C++ file.

PiperOrigin-RevId: 827850819
Change-Id: I23e099d4e72557d79354339953246ac4eeee7ca3

wasm/codegen/helpers/constants.py

@@ -420,7 +420,7 @@ MJDATA_SIZES = [
 ]
 
 # Dictionary where keys are the struct names and the values are lists of the
-# fields that are manually specified in the structs.h template file.
+# fields that are manually specified in the bindings.cc template file.
 MANUALLY_ADDED_FIELDS_FROM_TEMPLATE = {
     # go/keep-sorted start
     "MjData": ["solver", "timer", "warning", "contact"],

wasm/codegen/helpers/struct_constructor_code_builder.py

@@ -77,7 +77,8 @@ def _build_struct_header_internal(
     builder.line("")
     builder.line("private:")
     builder.line(f"{struct_name}* ptr_;")
-    builder.line("bool owned_ = false;")
+    if not is_mjs:
+      builder.line("bool owned_ = false;")
 
     if is_mjs and fields_with_init:
       builder.line("")