Fix missing cases of empty_string canonicalization

src/arm/macro-assembler-arm.h

Index: src/arm/macro-assembler-arm.h
diff --git a/src/arm/macro-assembler-arm.h b/src/arm/macro-assembler-arm.h
index 6216dfcd60618f7ea08b27cd3c8645225d2d11a7..e6765cd8ea443c8e4f1cce6433ebed9566432a8b 100644
--- a/src/arm/macro-assembler-arm.h
+++ b/src/arm/macro-assembler-arm.h
@@ -1431,12 +1431,6 @@ class MacroAssembler: public Assembler {
                       InvokeFlag flag,
                       const CallWrapper& call_wrapper);
 
-  void InitializeNewString(Register string,
-                           Register length,
-                           Heap::RootListIndex map_index,
-                           Register scratch1,
-                           Register scratch2);
-
   // Helper for implementing JumpIfNotInNewSpace and JumpIfInNewSpace.
   void InNewSpace(Register object,
                   Register scratch,