fix warnings
Review URL: https://codereview.appspot.com/7060053

git-svn-id: http://skia.googlecode.com/svn/trunk@7070 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tools/bench_pictures_main.cpp b/tools/bench_pictures_main.cpp
index 65fc42a..73c9a7d 100644
--- a/tools/bench_pictures_main.cpp
+++ b/tools/bench_pictures_main.cpp
@@ -450,7 +450,7 @@
                 gLogger.logError("Missing scaleFactor for --scale\n");
                 PRINT_USAGE_AND_EXIT;
             }
-            scaleFactor = atof(*argv);
+            scaleFactor = SkDoubleToScalar(atof(*argv));
         } else if (0 == strcmp(*argv, "--tiles")) {
             ++argv;
             if (argv >= stop) {