[ADT/StringMap] Follow-up to r172455, use the correct constructor for…

… setting the InitialSize,

previously it was calling the "StringMapImpl(unsigned itemSize)" constructor.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172500 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ADT/StringMap.h

@@ -238,7 +238,8 @@ class StringMap : public StringMapImpl {
     : StringMapImpl(static_cast<unsigned>(sizeof(MapEntryTy))), Allocator(A) {}
 
   StringMap(unsigned InitialSize, AllocatorTy A)
-    : StringMapImpl(InitialSize), Allocator(A) {}
+    : StringMapImpl(InitialSize, static_cast<unsigned>(sizeof(MapEntryTy))),
+      Allocator(A) {}
 
   StringMap(const StringMap &RHS)
     : StringMapImpl(static_cast<unsigned>(sizeof(MapEntryTy))) {