[heap] Do not trace through blink after making weak roots strong for finalizers

src/heap/mark-compact.cc

 // Copyright 2012 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/mark-compact.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/base/sys-info.h"
 #include "src/code-stubs.h"
@@ skipping 2122 matching lines @@
   DCHECK(marking_deque()->IsEmpty());
 }
 
 // Mark all objects reachable (transitively) from objects on the marking
 // stack including references only considered in the atomic marking pause.
 void MarkCompactCollector::ProcessEphemeralMarking(
     ObjectVisitor* visitor, bool only_process_harmony_weak_collections) {
   DCHECK(marking_deque()->IsEmpty() && !marking_deque()->overflowed());
   bool work_to_do = true;
   while (work_to_do) {
-    if (heap_->UsingEmbedderHeapTracer()) {
-      TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_WRAPPER_TRACING);
-      heap_->RegisterWrappersWithEmbedderHeapTracer();
-      heap_->embedder_heap_tracer()->AdvanceTracing(
-          0, EmbedderHeapTracer::AdvanceTracingActions(
-                 EmbedderHeapTracer::ForceCompletionAction::FORCE_COMPLETION));
-    }
     if (!only_process_harmony_weak_collections) {
-      TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_OBJECT_GROUPING);
-      isolate()->global_handles()->IterateObjectGroups(
-          visitor, &IsUnmarkedHeapObjectWithHeap);
-      MarkImplicitRefGroups(&MarkCompactMarkingVisitor::MarkObject);
+      if (heap_->UsingEmbedderHeapTracer()) {
+        TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_WRAPPER_TRACING);
+        heap_->RegisterWrappersWithEmbedderHeapTracer();
+        heap_->embedder_heap_tracer()->AdvanceTracing(
+            0,
+            EmbedderHeapTracer::AdvanceTracingActions(
+                EmbedderHeapTracer::ForceCompletionAction::FORCE_COMPLETION));
+      } else {
+        TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_OBJECT_GROUPING);
+        isolate()->global_handles()->IterateObjectGroups(
+            visitor, &IsUnmarkedHeapObjectWithHeap);
+        MarkImplicitRefGroups(&MarkCompactMarkingVisitor::MarkObject);
+      }
+    } else {
+      // TODO(mlippautz): We currently do not trace through blink when
+      // discovering new objects reachable from weak roots (that have been made
+      // strong). This is a limitation of not having a separate handle type
+      // that doesn't require zapping before this phase. See crbug.com/668060.
+      heap_->clear_wrappers_to_trace();
     }
     ProcessWeakCollections();
     work_to_do = !marking_deque()->IsEmpty();
     ProcessMarkingDeque<MarkCompactMode::FULL>();
   }
+  CHECK(heap_->MarkingDequesAreEmpty());
 }
 
 void MarkCompactCollector::ProcessTopOptimizedFrame(ObjectVisitor* visitor) {
   for (StackFrameIterator it(isolate(), isolate()->thread_local_top());
        !it.done(); it.Advance()) {
     if (it.frame()->type() == StackFrame::JAVA_SCRIPT) {
       return;
     }
     if (it.frame()->type() == StackFrame::OPTIMIZED) {
       Code* code = it.frame()->LookupCode();
@@ skipping 1909 matching lines @@
       // The target is always in old space, we don't have to record the slot in
       // the old-to-new remembered set.
       DCHECK(!heap()->InNewSpace(target));
       RecordRelocSlot(host, &rinfo, target);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8