Fix visualbench flicker on triple buffered platforms

tools/VisualBench/VisualStreamTimingModule.cpp

Index: tools/VisualBench/VisualStreamTimingModule.cpp
diff --git a/tools/VisualBench/VisualStreamTimingModule.cpp b/tools/VisualBench/VisualStreamTimingModule.cpp
index cb748ca5d825619d18119b377668e0d6a3d3a132..0ac698eff203de5a416edbdb16a123f6288ea1b0 100644
--- a/tools/VisualBench/VisualStreamTimingModule.cpp
+++ b/tools/VisualBench/VisualStreamTimingModule.cpp
@@ -25,7 +25,7 @@ inline void VisualStreamTimingModule::handleInitState(SkCanvas* canvas) {
         case kReset_InitState:
             // This will flicker unfortunately, but as we are reseting the GLContext each bench,
             // we unfortunately don't have a choice
-            fOwner->clear(canvas, SK_ColorWHITE, 2);
+            fOwner->clear(canvas, SK_ColorWHITE, 3);
             fBenchmarkStream->current()->preTimingHooks(canvas);
             break;
         case kNone_InitState: