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

src/gpu/GrRecordReplaceDraw.cpp

Index: src/gpu/GrRecordReplaceDraw.cpp
diff --git a/src/gpu/GrRecordReplaceDraw.cpp b/src/gpu/GrRecordReplaceDraw.cpp
index 1fe60407895ac8bebe67d3f24687c6ad0c4d4b8a..4d793904f4e59bc2ce36026ff69423ca4c65a4f1 100644
--- a/src/gpu/GrRecordReplaceDraw.cpp
+++ b/src/gpu/GrRecordReplaceDraw.cpp
@@ -99,7 +99,7 @@ public:
                     return fNumReplaced;
                 }
 
-                record->visit<void>(fOps[fIndex], *this);
+                record->visit(fOps[fIndex], *this);
             }
 
         } else {
@@ -108,7 +108,7 @@ public:
                     return fNumReplaced;
                 }
 
-                record->visit<void>(fIndex, *this);
+                record->visit(fIndex, *this);
             }
         }