[wasm] Initialize the root register for WASM tests.

src/x87/macro-assembler-x87.h

Index: src/x87/macro-assembler-x87.h
diff --git a/src/x87/macro-assembler-x87.h b/src/x87/macro-assembler-x87.h
index 855852b940331c2b40d75973439cb546df36696b..efab3f789097ef3c5de5e148940d49c3647693a4 100644
--- a/src/x87/macro-assembler-x87.h
+++ b/src/x87/macro-assembler-x87.h
@@ -271,6 +271,9 @@ class MacroAssembler: public Assembler {
   void StoreToSafepointRegisterSlot(Register dst, Immediate src);
   void LoadFromSafepointRegisterSlot(Register dst, Register src);
 
+  // Nop, because x87 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);