Make TestJSArrayForAllocationMemento less awkward.

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 931a4eb12fac3baf70b1ff86f5311174832991b3..d1c24343628d6f3d37e89c9b0a66b244875544d8 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -1412,9 +1412,20 @@ class MacroAssembler: public Assembler {
   // to another type.
   // On entry, receiver_reg should point to the array object.
   // scratch_reg gets clobbered.
-  // If allocation info is present, condition flags are set to equal
+  // If allocation info is present, condition flags are set to equal.
   void TestJSArrayForAllocationMemento(Register receiver_reg,
-                                       Register scratch_reg);
+                                       Register scratch_reg,
+                                       Label* no_memento_found);
+
+  void JumpIfJSArrayHasAllocationMemento(Register receiver_reg,
+                                         Register scratch_reg,
+                                         Label* memento_found) {
+    Label no_memento_found;
+    TestJSArrayForAllocationMemento(receiver_reg, scratch_reg,
+                                    &no_memento_found);
+    j(equal, memento_found);
+    bind(&no_memento_found);
+  }
 
  private:
   // Order general registers are pushed by Pushad.