Add NVPR to VisualBench

BUG=skia:

Review URL: https://codereview.chromium.org/1409603004
diff --git a/tools/VisualBench/VisualBench.cpp b/tools/VisualBench/VisualBench.cpp
index 39d2491..9cc2ec1 100644
--- a/tools/VisualBench/VisualBench.cpp
+++ b/tools/VisualBench/VisualBench.cpp
@@ -84,8 +84,10 @@
 
     fInterface.reset(GrGLCreateNativeInterface());
 
-    // TODO use the GLContext creation factories
-    fInterface.reset(GrGLInterfaceRemoveNVPR(fInterface));
+    // TODO use the GLContext creation factories and also set this all up in configs
+    if (!FLAGS_nvpr) {
+        fInterface.reset(GrGLInterfaceRemoveNVPR(fInterface));
+    }
     SkASSERT(fInterface);
 
     // setup contexts