[heap] Ensure progress when incrementally marking wrappers

src/heap/embedder-tracing.cc

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/embedder-tracing.h"
 
 #include "src/base/logging.h"
 
 namespace v8 {
 namespace internal {
 
 void LocalEmbedderHeapTracer::TracePrologue() {
   if (!InUse()) return;
 
   CHECK(cached_wrappers_to_trace_.empty());
+  num_v8_marking_deque_was_empty_ = 0;
+  in_final_pause_ = false;
   remote_tracer_->TracePrologue();
 }
 
 void LocalEmbedderHeapTracer::TraceEpilogue() {
   if (!InUse()) return;
 
   CHECK(cached_wrappers_to_trace_.empty());
   remote_tracer_->TraceEpilogue();
 }
 
 void LocalEmbedderHeapTracer::AbortTracing() {
   if (!InUse()) return;
 
   cached_wrappers_to_trace_.clear();
   remote_tracer_->AbortTracing();
 }
 
 void LocalEmbedderHeapTracer::EnterFinalPause() {
   if (!InUse()) return;
 
+  in_final_pause_ = true;
   remote_tracer_->EnterFinalPause();
 }
 
 bool LocalEmbedderHeapTracer::Trace(
     double deadline, EmbedderHeapTracer::AdvanceTracingActions actions) {
   if (!InUse()) return false;
 
   RegisterWrappersWithRemoteTracer();
-  return remote_tracer_->AdvanceTracing(deadline, actions);
+  return (in_final_pause_ ||
+          (num_v8_marking_deque_was_empty_ <= kMaxIncrementalMarkingRounds))
+             ? remote_tracer_->AdvanceTracing(deadline, actions)
+             : false;
 }
 
 size_t LocalEmbedderHeapTracer::NumberOfWrappersToTrace() {
   return (InUse())
              ? cached_wrappers_to_trace_.size() +
                    remote_tracer_->NumberOfWrappersToTrace()
              : 0;
 }
 
 void LocalEmbedderHeapTracer::RegisterWrappersWithRemoteTracer() {
   if (!InUse()) return;
 
   if (cached_wrappers_to_trace_.empty()) {
     return;
   }
 
   remote_tracer_->RegisterV8References(cached_wrappers_to_trace_);
   cached_wrappers_to_trace_.clear();
 }
 
 bool LocalEmbedderHeapTracer::RequiresImmediateWrapperProcessing() {
   const size_t kTooManyWrappers = 16000;
   return cached_wrappers_to_trace_.size() > kTooManyWrappers;
 }
 
 }  // namespace internal
 }  // namespace v8