Oilpan: We shouldn't trigger too many conservative GCs when detaching iframes

third_party/WebKit/Source/platform/heap/ThreadState.cpp

Index: third_party/WebKit/Source/platform/heap/ThreadState.cpp
diff --git a/third_party/WebKit/Source/platform/heap/ThreadState.cpp b/third_party/WebKit/Source/platform/heap/ThreadState.cpp
index 9222e8bb75494167a15e14433158469e96e62842..d0303fafe1e8c8e7694a70d13570fd365f143267 100644
--- a/third_party/WebKit/Source/platform/heap/ThreadState.cpp
+++ b/third_party/WebKit/Source/platform/heap/ThreadState.cpp
@@ -99,6 +99,7 @@ ThreadState::ThreadState()
     , m_gcForbiddenCount(0)
     , m_persistentAllocated(0)
     , m_persistentFreed(0)
+    , m_disposedV8ContextCount(0)
     , m_vectorBackingHeapIndex(Vector1HeapIndex)
     , m_currentHeapAges(0)
     , m_isTerminating(false)
@@ -731,6 +732,27 @@ void ThreadState::schedulePageNavigationGC()
     setGCState(PageNavigationGCScheduled);
 }
 
+void ThreadState::v8ContextCreated()
+{
+    if (m_disposedV8ContextCount >= 5) {
+        // A frame retains a lot of memory in the V8 side. V8's GC cannot
+        // collect the memory until Oilpan's GC collects the frame. So we
+        // force a conservative GC if no Oilpan's GC has been observed in
+        // the past 5 frame navigations.
+        //
+        // We force a conservative GC not in v8ContextDisposed but in
+        // v8ContextCreated. This avoids triggering too many conservative
+        // GCs when a frame that has a lot of iframes gets detached.
+        Heap::collectGarbage(HeapPointersOnStack, GCWithoutSweep, Heap::ConservativeGC);
+        return;
+    }
+}
+
+void ThreadState::v8ContextDisposed()
+{
+    ++m_disposedV8ContextCount;
+}
+
 void ThreadState::scheduleGCIfNeeded()
 {
     ASSERT(checkThread());
@@ -1003,6 +1025,7 @@ void ThreadState::preGC()
     flushHeapDoesNotContainCacheIfNeeded();
     clearHeapAges();
     updatePersistentCounters();
+    m_disposedV8ContextCount = 0;
 }
 
 void ThreadState::postGC(GCType gcType)