Revert "viz: Add temp CHECKs for debugging."

This reverts commit 1ba39268.

Reason for revert: Change was temporary to aid debugging.

Original change's description:
> viz: Add temp CHECKs for debugging.
> 
> R=​kylechar@chromium.org
> 
> Bug: 992626
> Change-Id: If13d2f4c9660c49db82e586929b2686b54f3760a
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1797128
> Commit-Queue: Khushal <khushalsagar@chromium.org>
> Commit-Queue: kylechar <kylechar@chromium.org>
> Auto-Submit: Khushal <khushalsagar@chromium.org>
> Reviewed-by: kylechar <kylechar@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#695430}

TBR=khushalsagar@chromium.org,kylechar@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 992626
Change-Id: I6388a12e22a85c8b24dacf9bb992eeeb933da101
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1848359Reviewed-by: Khushal <khushalsagar@chromium.org>
Commit-Queue: Khushal <khushalsagar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#703962}

base/callback_helpers.h

@@ -114,8 +114,6 @@ class BASE_EXPORT ScopedClosureRunner {
   // Releases the Closure without calling.
   OnceClosure Release() WARN_UNUSED_RESULT;
 
-  bool is_null() const { return closure_.is_null(); }
-
  private:
   OnceClosure closure_;
 

components/viz/service/frame_sinks/frame_sink_manager_impl.cc

@@ -633,18 +633,15 @@ void FrameSinkManagerImpl::CacheBackBuffer(
   auto it = root_sink_map_.find(root_frame_sink_id);
 
   DCHECK(it != root_sink_map_.end());
-  // TODO(khushalsagar) : Temp CHECKs for debugging. See crbug.com/992626.
-  CHECK(cached_back_buffers_.find(cache_id) == cached_back_buffers_.end());
+  DCHECK(cached_back_buffers_.find(cache_id) == cached_back_buffers_.end());
 
   cached_back_buffers_[cache_id] = it->second->GetCacheBackBufferCb();
-  CHECK(!cached_back_buffers_[cache_id].is_null());
 }
 
 void FrameSinkManagerImpl::EvictBackBuffer(uint32_t cache_id,
                                            EvictBackBufferCallback callback) {
   auto it = cached_back_buffers_.find(cache_id);
-  // TODO(khushalsagar) : Temp CHECKs for debugging. See crbug.com/992626.
-  CHECK(it != cached_back_buffers_.end());
+  DCHECK(it != cached_back_buffers_.end());
 
   it->second.RunAndReset();
   cached_back_buffers_.erase(it);