Move some work from backend onClear to base class clear

src/gpu/GrTest.cpp

Index: src/gpu/GrTest.cpp
diff --git a/src/gpu/GrTest.cpp b/src/gpu/GrTest.cpp
index f77092ae7e96858a694d6e40a45556de853881d5..518ebacc0786ae86e50c2896469614bfec8b14b0 100644
--- a/src/gpu/GrTest.cpp
+++ b/src/gpu/GrTest.cpp
@@ -202,8 +202,7 @@ private:
 
     GrIndexBuffer* onCreateIndexBuffer(size_t size, bool dynamic) override { return NULL; }
 
-    void onClear(GrRenderTarget*, const SkIRect* rect, GrColor color,
-                         bool canIgnoreRect) override {}
+    void onClear(GrRenderTarget*, const SkIRect& rect, GrColor color) override {}
 
     void onClearStencilClip(GrRenderTarget*, const SkIRect& rect, bool insideClip) override {}