add roundOut that returns its result

BUG=skia:

Review URL: https://codereview.chromium.org/742663002
diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index 8d17be7..4fda7a3 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -1586,9 +1586,7 @@
     if (fMCRec->fMatrix.hasPerspective()) {
         SkRect dst;
         fMCRec->fMatrix.mapRect(&dst, rect);
-        SkIRect idst;
-        dst.roundOut(&idst);
-        return !SkIRect::Intersects(idst, fMCRec->fRasterClip.getBounds());
+        return !SkIRect::Intersects(dst.roundOut(), fMCRec->fRasterClip.getBounds());
     } else {
         const SkRect& clipR = this->getLocalClipBounds();