Just visit young array buffers during scavenge.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index cec871403a718d8f2a88b8666af713e48ba56f54..ddaa70e94676db31bc84b44b6219be8117878886 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -106,6 +106,8 @@ Heap::Heap()
       old_generation_allocation_limit_(initial_old_generation_size_),
       old_gen_exhausted_(false),
       inline_allocation_disabled_(false),
+      last_array_buffers_young_object_(NULL),
+      last_native_contexts_young_object_(NULL),
       store_buffer_rebuilder_(store_buffer()),
       hidden_string_(NULL),
       gc_safe_size_of_old_object_(NULL),
@@ -1690,29 +1692,38 @@ void Heap::UpdateReferencesInExternalStringTable(
 
 
 void Heap::ProcessAllWeakReferences(WeakObjectRetainer* retainer) {
-  ProcessArrayBuffers(retainer);
-  ProcessNativeContexts(retainer);
+  ProcessArrayBuffers(retainer, NULL);
+  ProcessNativeContexts(retainer, NULL);
   ProcessAllocationSites(retainer);
 }
 
 
 void Heap::ProcessYoungWeakReferences(WeakObjectRetainer* retainer) {
-  ProcessArrayBuffers(retainer);
-  ProcessNativeContexts(retainer);
+  ProcessArrayBuffers(retainer, last_array_buffers_young_object_);
+  ProcessNativeContexts(retainer, last_native_contexts_young_object_);
 }
 
 
-void Heap::ProcessNativeContexts(WeakObjectRetainer* retainer) {
-  Object* head = VisitWeakList<Context>(this, native_contexts_list(), retainer);
+void Heap::ProcessNativeContexts(WeakObjectRetainer* retainer,
+                                 Object* last_native_contexts_young_object) {
+  Object* last_young_object_recorded = NULL;
+  Object* head = VisitWeakList<Context>(this, native_contexts_list(), retainer,
+                                        last_native_contexts_young_object,
+                                        &last_young_object_recorded);

[ulan, 2015/02/03 11:15:21]

It just occurred to me that this won't work because of weak list hanging off the
native contexts (list of optimized functions for example). We need to process
all of them even if they are in old space because optimized functions can in new
space.

   // Update the head of the list of contexts.
   set_native_contexts_list(head);
+  last_native_contexts_young_object_ = last_young_object_recorded;
 }
 
 
-void Heap::ProcessArrayBuffers(WeakObjectRetainer* retainer) {
-  Object* array_buffer_obj =
-      VisitWeakList<JSArrayBuffer>(this, array_buffers_list(), retainer);
+void Heap::ProcessArrayBuffers(WeakObjectRetainer* retainer,
+                               Object* last_array_buffers_young_object) {
+  Object* last_young_object_recorded = NULL;
+  Object* array_buffer_obj = VisitWeakList<JSArrayBuffer>(
+      this, array_buffers_list(), retainer, last_array_buffers_young_object,
+      &last_young_object_recorded);
   set_array_buffers_list(array_buffer_obj);
+  last_array_buffers_young_object_ = last_young_object_recorded;
 }
 
 
@@ -1728,8 +1739,8 @@ void Heap::TearDownArrayBuffers() {
 
 
 void Heap::ProcessAllocationSites(WeakObjectRetainer* retainer) {
-  Object* allocation_site_obj =
-      VisitWeakList<AllocationSite>(this, allocation_sites_list(), retainer);
+  Object* allocation_site_obj = VisitWeakList<AllocationSite>(
+      this, allocation_sites_list(), retainer, NULL, NULL);
   set_allocation_sites_list(allocation_site_obj);
 }