Hide WasmModule.origin field behind readable accessors.

test/unittests/wasm/function-body-decoder-unittest.cc

Index: test/unittests/wasm/function-body-decoder-unittest.cc
diff --git a/test/unittests/wasm/function-body-decoder-unittest.cc b/test/unittests/wasm/function-body-decoder-unittest.cc
index 5e382f92de5b3320c1767c5a6c40a85d4d1aefb2..0b54175fef23e1f1460569c640d061ff80bddfb3 100644
--- a/test/unittests/wasm/function-body-decoder-unittest.cc
+++ b/test/unittests/wasm/function-body-decoder-unittest.cc
@@ -211,7 +211,7 @@ class TestModuleEnv : public ModuleEnv {
  public:
   explicit TestModuleEnv(ModuleOrigin origin = kWasmOrigin)
       : ModuleEnv(&mod, nullptr) {
-    mod.origin = origin;
+    mod.set_origin(origin);
   }
   byte AddGlobal(ValueType type, bool mutability = true) {
     mod.globals.push_back({type, mutability, WasmInitExpr(), 0, false, false});