Oilpan: DOM wrappers don't need to keep persistent handles

Source/platform/heap/ThreadState.cpp

Index: Source/platform/heap/ThreadState.cpp
diff --git a/Source/platform/heap/ThreadState.cpp b/Source/platform/heap/ThreadState.cpp
index a8528379ef8d18f4e9ee698beaed244cb4250ed0..60f6eca1fd0e166c6b6cb9ebf9d25e059b081568 100644
--- a/Source/platform/heap/ThreadState.cpp
+++ b/Source/platform/heap/ThreadState.cpp
@@ -134,10 +134,6 @@ static size_t getUnderestimatedStackSize()
 #endif
 }
 
-// The maximum number of WrapperPersistentRegions to keep around in the
-// m_pooledWrapperPersistentRegions pool.
-static const size_t MaxPooledWrapperPersistentRegionCount = 2;
-
 WTF::ThreadSpecific<ThreadState*>* ThreadState::s_threadSpecific = 0;
 uintptr_t ThreadState::s_mainThreadStackStart = 0;
 uintptr_t ThreadState::s_mainThreadUnderestimatedStackSize = 0;
@@ -325,9 +321,6 @@ template<> struct InitializeHeaps<0> {
 
 ThreadState::ThreadState()
     : m_thread(currentThread())
-    , m_liveWrapperPersistents(new WrapperPersistentRegion())
-    , m_pooledWrapperPersistents(0)
-    , m_pooledWrapperPersistentRegionCount(0)
     , m_persistents(adoptPtr(new PersistentAnchor()))
     , m_startOfStack(reinterpret_cast<intptr_t*>(getStackStart()))
     , m_endOfStack(reinterpret_cast<intptr_t*>(getStackStart()))
@@ -344,6 +337,7 @@ ThreadState::ThreadState()
     , m_shouldFlushHeapDoesNotContainCache(false)
     , m_lowCollectionRate(false)
     , m_numberOfSweeperTasks(0)
+    , m_traceDOMWrappers(0)
 #if defined(ADDRESS_SANITIZER)
     , m_asanFakeStack(__asan_get_current_fake_stack())
 #endif
@@ -372,14 +366,6 @@ ThreadState::~ThreadState()
     for (int i = 0; i < NumberOfHeaps; i++)
         delete m_heaps[i];
     deleteAllValues(m_interruptors);
-    while (m_liveWrapperPersistents) {
-        WrapperPersistentRegion* region = WrapperPersistentRegion::removeHead(&m_liveWrapperPersistents);
-        delete region;
-    }
-    while (m_pooledWrapperPersistents) {
-        WrapperPersistentRegion* region = WrapperPersistentRegion::removeHead(&m_pooledWrapperPersistents);
-        delete region;
-    }
     **s_threadSpecific = 0;
     s_mainThreadStackStart = 0;
     s_mainThreadUnderestimatedStackSize = 0;
@@ -617,9 +603,9 @@ void ThreadState::visitStack(Visitor* visitor)
 void ThreadState::visitPersistents(Visitor* visitor)
 {
     m_persistents->trace(visitor);
-    {
-        TRACE_EVENT0("blink_gc", "WrapperPersistentRegion::trace");
-        WrapperPersistentRegion::trace(m_liveWrapperPersistents, visitor);
+    if (m_traceDOMWrappers) {
+        TRACE_EVENT0("blink_gc", "V8GCController::traceDOMWrappers");
+        m_traceDOMWrappers(m_isolate, visitor);
     }
 }
 
@@ -728,34 +714,6 @@ bool ThreadState::popAndInvokeWeakPointerCallback(Visitor* visitor)
     return false;
 }
 
-WrapperPersistentRegion* ThreadState::takeWrapperPersistentRegion()
-{
-    WrapperPersistentRegion* region;
-    if (m_pooledWrapperPersistentRegionCount) {
-        region = WrapperPersistentRegion::removeHead(&m_pooledWrapperPersistents);
-        m_pooledWrapperPersistentRegionCount--;
-    } else {
-        region = new WrapperPersistentRegion();
-    }
-    ASSERT(region);
-    WrapperPersistentRegion::insertHead(&m_liveWrapperPersistents, region);
-    return region;
-}
-
-void ThreadState::freeWrapperPersistentRegion(WrapperPersistentRegion* region)
-{
-    if (!region->removeIfNotLast(&m_liveWrapperPersistents))
-        return;
-
-    // Region was removed, ie. it was not the last region in the list.
-    if (m_pooledWrapperPersistentRegionCount < MaxPooledWrapperPersistentRegionCount) {
-        WrapperPersistentRegion::insertHead(&m_pooledWrapperPersistents, region);
-        m_pooledWrapperPersistentRegionCount++;
-    } else {
-        delete region;
-    }
-}
-
 PersistentNode* ThreadState::globalRoots()
 {
     AtomicallyInitializedStatic(PersistentNode*, anchor = new PersistentAnchor);