[wasm] Initialize the root register for WASM tests.

src/ia32/macro-assembler-ia32.h

Index: src/ia32/macro-assembler-ia32.h
diff --git a/src/ia32/macro-assembler-ia32.h b/src/ia32/macro-assembler-ia32.h
index 04788362c3e95571caea12d1e8927b6ad823afe8..b819d7a5f507e1c52a7674634ede9487750a4749 100644
--- a/src/ia32/macro-assembler-ia32.h
+++ b/src/ia32/macro-assembler-ia32.h
@@ -271,6 +271,9 @@ class MacroAssembler: public Assembler {
   void StoreToSafepointRegisterSlot(Register dst, Immediate src);
   void LoadFromSafepointRegisterSlot(Register dst, Register src);
 
+  // Nop, because ia32 does not have a root register.
+  void InitializeRootRegister() {}
+
   void LoadHeapObject(Register result, Handle<HeapObject> object);
   void CmpHeapObject(Register reg, Handle<HeapObject> object);
   void PushHeapObject(Handle<HeapObject> object);