Revert "Clean up stale cache entries in Skia's GrContext (flutter#6859)…

…" (flutter#6866)

This reverts commit 2c6be93.

shell/common/rasterizer.cc

@@ -16,10 +16,6 @@
 
 namespace shell {
 
-// The rasterizer will tell Skia to purge cached resources that have not been
-// used within this interval.
-static constexpr std::chrono::milliseconds kSkiaCleanupExpiration(15000);
-
 Rasterizer::Rasterizer(blink::TaskRunners task_runners)
     : Rasterizer(std::move(task_runners),
                  std::make_unique<flow::CompositorContext>()) {}
@@ -190,9 +186,6 @@ bool Rasterizer::DrawToSurface(flow::LayerTree& layer_tree) {
       external_view_embedder->SubmitFrame(surface_->GetContext());
     }
     FireNextFrameCallbackIfPresent();
-
-    surface_->GetContext()->performDeferredCleanup(kSkiaCleanupExpiration);
-
     return true;
   }