Flush GrContext between benchmark draw loops

This change updates a small subset of benchmarks to flush the GrContext
between draw loops (specifically SKP benchmarks, SampleApp, and the
warmup in visualbench). This helps improve timing accuracy by not
allowing the gpu to batch across draw boundaries in the affected
benchmarks.

BUG=skia:

Review URL: https://codereview.chromium.org/1427533002

1 files changed, 6 insertions, 0 deletions

diff --git a/samplecode/SampleApp.cpp b/samplecode/SampleApp.cpp
index 9be7567ea0..07a7a87b7f 100644
--- a/samplecode/SampleApp.cpp
+++ b/samplecode/SampleApp.cpp
@@ -2257,6 +2257,12 @@ void SampleView::onDraw(SkCanvas* canvas) {
     for (int i = 0; i < fRepeatCount; i++) {
         SkAutoCanvasRestore acr(canvas, true);
         this->onDrawContent(canvas);
+#if SK_SUPPORT_GPU
+        // Ensure the GrContext doesn't batch across draw loops.
+        if (GrContext* context = canvas->getGrContext()) {
+            context->flush();
+        }
+#endif
     }
 }