From f2af347363ddb5b4ed9598b285d4f5ce000331d5 Mon Sep 17 00:00:00 2001
From: Chinmay Garde <chinmaygarde@gmail.com>
Date: Mon, 31 Jul 2017 15:16:48 -0700
Subject: [PATCH] Always consume items from the pipeline in the null
 rasterizer. (#3937)

Now, frame requests past the pipeline depth will never be deferred due
to back pressure. This backend is only used in the test runner.
---
 shell/common/null_rasterizer.cc | 7 ++++++-
 shell/common/null_rasterizer.h  | 2 +-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/shell/common/null_rasterizer.cc b/shell/common/null_rasterizer.cc
index 670e4238038..81c0e1f458b 100644
--- a/shell/common/null_rasterizer.cc
+++ b/shell/common/null_rasterizer.cc
@@ -39,7 +39,12 @@ void NullRasterizer::Clear(SkColor color, const SkISize& size) {
 
 void NullRasterizer::Draw(
     ftl::RefPtr<flutter::Pipeline<flow::LayerTree>> pipeline) {
-  // Null rasterizer. Nothing to do.
+  FTL_ALLOW_UNUSED_LOCAL(
+      pipeline->Consume([](std::unique_ptr<flow::LayerTree>) {
+        // Drop the layer tree on the floor. We only need the pipeline empty so
+        // that frame requests are not deferred indefinitely due to
+        // backpressure.
+      }));
 }
 
 }  // namespace shell
diff --git a/shell/common/null_rasterizer.h b/shell/common/null_rasterizer.h
index 4b120a9d304..eba9a57e4f3 100644
--- a/shell/common/null_rasterizer.h
+++ b/shell/common/null_rasterizer.h
@@ -31,8 +31,8 @@ class NullRasterizer : public Rasterizer {
   void Draw(ftl::RefPtr<flutter::Pipeline<flow::LayerTree>> pipeline) override;
 
  private:
-  ftl::WeakPtrFactory<NullRasterizer> weak_factory_;
   std::unique_ptr<Surface> surface_;
+  ftl::WeakPtrFactory<NullRasterizer> weak_factory_;
 
   FTL_DISALLOW_COPY_AND_ASSIGN(NullRasterizer);
 };