exo::CompositorFrameSinkHolder's release callbacks hold ref

components/exo/compositor_frame_sink_holder.cc

Index: components/exo/compositor_frame_sink_holder.cc
diff --git a/components/exo/compositor_frame_sink_holder.cc b/components/exo/compositor_frame_sink_holder.cc
index dcd3110ab6ea9cb7a03a31a22d1e5b44cb906787..112b02530f3d89b6b903dc9200f128f06944fd16 100644
--- a/components/exo/compositor_frame_sink_holder.cc
+++ b/components/exo/compositor_frame_sink_holder.cc
@@ -4,7 +4,6 @@
 
 #include "components/exo/compositor_frame_sink_holder.h"
 
-#include "base/memory/ptr_util.h"
 #include "cc/resources/returned_resource.h"
 #include "components/exo/surface.h"
 
@@ -33,7 +32,7 @@ bool CompositorFrameSinkHolder::HasReleaseCallbackForResource(
 void CompositorFrameSinkHolder::AddResourceReleaseCallback(

[reveman, 2017/01/02 19:57:56]

nit: SetResourceReleaseCallback

     cc::ResourceId id,
     std::unique_ptr<cc::SingleReleaseCallback> callback) {
-  release_callbacks_[id] = std::make_pair(this, std::move(callback));
+  release_callbacks_[id] = std::move(callback);
 }
 
 void CompositorFrameSinkHolder::ActivateFrameCallbacks(
@@ -84,10 +83,12 @@ void CompositorFrameSinkHolder::ReclaimResources(
   for (auto& resource : resources) {
     auto it = release_callbacks_.find(resource.id);
     DCHECK(it != release_callbacks_.end());
-    std::unique_ptr<cc::SingleReleaseCallback> callback =
-        std::move(it->second.second);
+    bool will_run = base::ThreadTaskRunnerHandle::Get()->PostTask(

[reveman, 2017/01/02 19:57:56]

If you remove the reset of the sink holder in Buffer::CheckReleaseCallback then
I think we can finally do just this here:

auto it = release_callbacks_.find(resource.id);
DCHECK(it != release_callbacks_.end());
it->second->Run(resource.sync_token, resource.lost);
release_callbacks_.erase(it);

+        FROM_HERE, base::Bind(&cc::SingleReleaseCallback::Run,
+                              base::Passed(std::move(it->second)),
+                              resource.sync_token, resource.lost));
+    DCHECK(will_run);
     release_callbacks_.erase(it);
-    callback->Run(resource.sync_token, resource.lost);
   }
 }