Flush GrContext between benchmark draw loops

tools/VisualBench/VisualSKPBench.cpp

Index: tools/VisualBench/VisualSKPBench.cpp
diff --git a/tools/VisualBench/VisualSKPBench.cpp b/tools/VisualBench/VisualSKPBench.cpp
index 649d324a668474e69ed0e36ba44fc9f7546859f2..628265e53e103d9a485fd4d5c6dc76fc01c960a8 100644
--- a/tools/VisualBench/VisualSKPBench.cpp
+++ b/tools/VisualBench/VisualSKPBench.cpp
@@ -8,6 +8,10 @@
 
 #include "VisualSKPBench.h"
 
+#if SK_SUPPORT_GPU
+#include "GrContext.h"
+#endif
+
 VisualSKPBench::VisualSKPBench(const char* name, const SkPicture* pic)
     : fPic(SkRef(pic))
     , fName(name) {
@@ -29,5 +33,11 @@ bool VisualSKPBench::isSuitableFor(Backend backend) {
 void VisualSKPBench::onDraw(int loops, SkCanvas* canvas) {
     for (int i = 0; i < loops; i++) {
         canvas->drawPicture(fPic);
+#if SK_SUPPORT_GPU
+        // Ensure the GrContext doesn't batch across draw loops.
+        if (GrContext* context = canvas->getGrContext()) {
+            context->flush();
+        }
+#endif
     }
 }