BackForwardCache: Allow WebScoket

Now the test harness was fixed, WebSocket should be available with
BackForwardCache.

Bug: 981740
Change-Id: I0adfaefac2032bb35e6e5488ed88f78fd979d877
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1690404Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Arthur Sonzogni <arthursonzogni@chromium.org>
Commit-Queue: Hajime Hoshi <hajimehoshi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#682651}

content/browser/frame_host/back_forward_cache.cc

@@ -30,7 +30,6 @@ constexpr uint64_t ToFeatureBit(WebSchedulerTrackedFeature feature) {
 // TODO(lowell): Finalize disallowed feature list, and test for each disallowed
 // feature.
 constexpr uint64_t kDisallowedFeatures =
-    ToFeatureBit(WebSchedulerTrackedFeature::kWebSocket) |
     ToFeatureBit(WebSchedulerTrackedFeature::kWebRTC) |
     ToFeatureBit(WebSchedulerTrackedFeature::kContainsPlugins) |
     ToFeatureBit(WebSchedulerTrackedFeature::kDedicatedWorkerOrWorklet) |