Add SwapPromise support to LayerTreeHost and LayerTreeImpl

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index df82093bd91fe977a23dbef3f69241721ea482fe..01dbe49f4d48151f84488a9ec51375b58de152db 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -385,6 +385,8 @@ void LayerTreeHost::FinishCommitOnImplThread(LayerTreeHostImpl* host_impl) {
   sync_tree->SetLatencyInfo(latency_info_);
   latency_info_.Clear();
 
+  sync_tree->PassSwapPromises(&swap_promise_list_);
+
   host_impl->SetViewportSize(device_viewport_size_);
   host_impl->SetOverdrawBottomHeight(overdraw_bottom_height_);
   host_impl->SetDeviceScaleFactor(device_scale_factor_);
@@ -1268,4 +1270,21 @@ bool LayerTreeHost::ScheduleMicroBenchmark(
       benchmark_name, value.Pass(), callback);
 }
 
+void LayerTreeHost::QueueSwapPromise(scoped_ptr<SwapPromise> swap_promise) {
+  if (proxy_->HasImplThread()) {
+    DCHECK(proxy_->CommitRequested() || proxy_->BeginMainFrameRequested());
+  }
+  if (swap_promise_list_.size() > kMaxQueuedSwapPromiseNumber)
+    BreakSwapPromises(SwapPromise::SWAP_PROMISE_LIST_OVERFLOW);
+  swap_promise_list_.push_back(swap_promise.Pass());
+}
+
+void LayerTreeHost::BreakSwapPromises(SwapPromise::DidNotSwapReason reason) {
+  for (size_t i = 0; i < swap_promise_list_.size(); i++) {
+    DCHECK(swap_promise_list_[i]);

[danakj, 2013/11/26 16:24:37]

Can you DCHECK this when they are added (QueueSwapPromise) instead of here? That
will find anything adding a NULL swap promise to the list faster, and give a
better stack trace. DCHECK before a null deref doesn't add too much value.

[Yufeng Shen (Slow to review), 2013/11/26 17:30:34]

Done.

+    swap_promise_list_[i]->DidNotSwap(reason);
+  }
+  swap_promise_list_.clear();
+}
+
 }  // namespace cc