Fix visualbench flicker on triple buffered platforms

tools/VisualBench/VisualStreamTimingModule.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "VisualStreamTimingModule.h"
 
 #include "SkCanvas.h"
 
 DEFINE_bool(reset, true, "Reset the GL context between samples.");
 
 VisualStreamTimingModule::VisualStreamTimingModule(VisualBench* owner)
     : fInitState(kReset_InitState)
     , fOwner(owner) {
     fBenchmarkStream.reset(new VisualBenchmarkStream(owner->getSurfaceProps()));
 }
 
 inline void VisualStreamTimingModule::handleInitState(SkCanvas* canvas) {
     switch (fInitState) {
         case kNewBenchmark_InitState:
             fBenchmarkStream->current()->delayedSetup();
             // fallthrough
         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:
             break;
     }
     fInitState = kNone_InitState;
 }
 
 inline void VisualStreamTimingModule::handleTimingEvent(SkCanvas* canvas,
                                                         TimingStateMachine::ParentEvents event) {
@@ skipping 31 matching lines @@
         // TODO research why this does happen on mac
         return;
     }
 
     this->handleInitState(canvas);
     this->renderFrame(canvas, fBenchmarkStream->current(), fTSM.loops());
     fOwner->present();
     TimingStateMachine::ParentEvents event = fTSM.nextFrame(FLAGS_reset);
     this->handleTimingEvent(canvas, event);
 }