SkRecord: infer return type for visit() and mutate().

tools/DumpRecord.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include <stdio.h>
 
 #include "SkRecord.h"
@@ skipping 50 matching lines @@
     }
 
     void print(const SkRecords::DrawPicture& command, double ns) {
         this->printNameAndTime(command, ns);
 
         if (auto bp = command.picture->asSkBigPicture()) {
             ++fIndent;
 
             const SkRecord& record = *bp->record();
             for (int i = 0; i < record.count(); i++) {
-                record.visit<void>(i, *this);
+                record.visit(i, *this);
             }
 
             --fIndent;
         }
     }
 
 private:
     template <typename T>
     void printNameAndTime(const T& command, double ns) {
         int us = (int)(ns * 1e-3);
@@ skipping 30 matching lines @@
     const bool fTimeWithCommand;
 };
 
 }  // namespace
 
 void DumpRecord(const SkRecord& record,
                   SkCanvas* canvas,
                   bool timeWithCommand) {
     Dumper dumper(canvas, record.count(), timeWithCommand);
     for (int i = 0; i < record.count(); i++) {
-        record.visit<void>(i, dumper);
+        record.visit(i, dumper);
     }
 }