add roundOut that returns its result

BUG=skia:

Review URL: https://codereview.chromium.org/742663002
diff --git a/src/effects/SkPictureImageFilter.cpp b/src/effects/SkPictureImageFilter.cpp
index 30fbac1..0c95b32 100644
--- a/src/effects/SkPictureImageFilter.cpp
+++ b/src/effects/SkPictureImageFilter.cpp
@@ -81,9 +81,8 @@
     }
 
     SkRect floatBounds;
-    SkIRect bounds;
     ctx.ctm().mapRect(&floatBounds, fCropRect);
-    floatBounds.roundOut(&bounds);
+    SkIRect bounds = floatBounds.roundOut();
     if (!bounds.intersect(ctx.clipBounds())) {
         return false;
     }