Eliminate one copy of replace_char() function.

tools/render_pictures_main.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "LazyDecodeBitmap.h"
 #include "CopyTilesRenderer.h"
 #include "SkBitmap.h"
@@ skipping 336 matching lines @@
                 SkDebugf("Number of pixels with max diff of %i is %i\n", i, diffs[i]);
             }
         }
     }
 
     if (FLAGS_writeWholeImage) {
         sk_tools::force_all_opaque(*bitmap);
 
         SkString inputFilename = SkOSPath::Basename(inputPath.c_str());
         SkString outputFilename(inputFilename);
-        sk_tools::replace_char(&outputFilename, '.', '_');
+        outputFilename.replace('.', '_');
         outputFilename.append(".png");
 
         if (jsonSummaryPtr) {
             sk_tools::ImageDigest imageDigest(*bitmap);
             jsonSummaryPtr->add(inputFilename.c_str(), outputFilename.c_str(), imageDigest);
             if ((mismatchPath) && !mismatchPath->isEmpty() &&
                 !jsonSummaryPtr->getExpectation(inputFilename.c_str()).matches(imageDigest)) {
                 success &= sk_tools::write_bitmap_to_disk(*bitmap, *mismatchPath, NULL,
                                                           outputFilename);
             }
@@ skipping 138 matching lines @@
         jsonSummary.writeToFile(FLAGS_writeJsonSummaryPath[0]);
     }
     return 0;
 }
 
 #if !defined SK_BUILD_FOR_IOS
 int main(int argc, char * const argv[]) {
     return tool_main(argc, (char**) argv);
 }
 #endif