Add matrix constructing helpers to SkMatrix

bench/SKPBench.cpp

Index: bench/SKPBench.cpp
diff --git a/bench/SKPBench.cpp b/bench/SKPBench.cpp
index 3f521799fa0d27af6e8f7a174137e1904df37e5d..6f74ff942d8aefbb7fbc86477e726b65abe9056f 100644
--- a/bench/SKPBench.cpp
+++ b/bench/SKPBench.cpp
@@ -116,9 +116,8 @@ void SKPBench::onDraw(const int loops, SkCanvas* canvas) {
     } else {
         for (int i = 0; i < loops; i++) {
             for (int j = 0; j < fTileRects.count(); ++j) {
-                SkMatrix trans;
-                trans.setTranslate(-fTileRects[j].fLeft / fScale,
-                                   -fTileRects[j].fTop / fScale);
+                const SkMatrix trans = SkMatrix::MakeTrans(-fTileRects[j].fLeft / fScale,
+                                                           -fTileRects[j].fTop / fScale);
                 fSurfaces[j]->getCanvas()->drawPicture(fPic, &trans, NULL);
             }