Make SkTDArray accessors const-friendly

src/pdf/SkPDFTypes.cpp

 
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkPDFCatalog.h"
@@ skipping 465 matching lines @@
     fValue.reset();
 }
 
 SkPDFDict::Iter::Iter(const SkPDFDict& dict)
     : fIter(dict.fValue.begin()),
       fStop(dict.fValue.end()) {
 }
 
 SkPDFName* SkPDFDict::Iter::next(SkPDFObject** value) {
     if (fIter != fStop) {
-        Rec* cur = fIter;
+        const Rec* cur = fIter;
         fIter++;
         *value = cur->value;
         return cur->key;
     }
     *value = NULL;
     return NULL;
 }