Fix non-ia32 build.

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
diff --git a/src/x64/macro-assembler-x64.h b/src/x64/macro-assembler-x64.h
index 1ee0fe0204f13cad8eb8627f1418240a3a9f00c1..9fde18dfa0035ee04b40cea6b66d084dd22b13b4 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -74,7 +74,11 @@ struct SmiIndex {
 // MacroAssembler implements a collection of frequently used macros.
 class MacroAssembler: public Assembler {
  public:
-  MacroAssembler(void* buffer, int size);
+  // The isolate parameter can be NULL if the macro assembler should
+  // not use isolate-dependent functionality. In this case, it's the
+  // responsibility of the caller to never invoke such function on the
+  // macro assembler.
+  MacroAssembler(Isolate* isolate, void* buffer, int size);
 
   // Prevent the use of the RootArray during the lifetime of this
   // scope object.
@@ -1029,7 +1033,10 @@ class MacroAssembler: public Assembler {
   // may be bigger than 2^16 - 1.  Requires a scratch register.
   void Ret(int bytes_dropped, Register scratch);
 
-  Handle<Object> CodeObject() { return code_object_; }
+  Handle<Object> CodeObject() {
+    ASSERT(!code_object_.is_null());
+    return code_object_;
+  }
 
   // Copy length bytes from source to destination.
   // Uses scratch register internally (if you have a low-eight register