Fix size_t to int conversion warning on Win64 in SkRTConf.h.

Review URL: https://codereview.chromium.org/23213004

git-svn-id: http://skia.googlecode.com/svn/trunk/include@10800 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/utils/SkRTConf.h b/utils/SkRTConf.h
index dc1f461..1dc41c9 100644
--- a/utils/SkRTConf.h
+++ b/utils/SkRTConf.h
@@ -115,10 +115,8 @@
     sprintf(outline, "%-30.30s", getName());
     doPrint(&(outline[30]));
     sprintf(&(outline[60]), " %.128s", fDescription.c_str());
-    if (' ' == outline[strlen(outline)-1]) {
-        for (int i = strlen(outline)-1 ; ' ' == outline[i] ; i--) {
-            outline[i] = '\0';
-        }
+    for (size_t i = strlen(outline); i --> 0 && ' ' == outline[i];) {
+        outline[i] = '\0';
     }
     o->writeText(outline);
 }