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/render_pictures_main.cpp b/tools/render_pictures_main.cpp
index e7ae036..e3e4318 100644
--- a/tools/render_pictures_main.cpp
+++ b/tools/render_pictures_main.cpp
@@ -425,7 +425,7 @@
                 usage(argv0);
                 exit(-1);
             }
-            scaleFactor = atof(*argv);
+            scaleFactor = SkDoubleToScalar(atof(*argv));
         } else if (0 == strcmp(*argv, "--tiles")) {
             ++argv;
             if (argv >= stop) {