We mustn't finalize sweeping when V8 started collecting garbage.

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 5dade81422fb90875c853471da1f73fa91d9e779..cd31f9cb92947993b8c3d798306abcd35d2953e4 100644
--- a/third_party/WebKit/Source/platform/heap/ThreadState.cpp
+++ b/third_party/WebKit/Source/platform/heap/ThreadState.cpp
@@ -630,29 +630,6 @@ void ThreadState::scheduleV8FollowupGCIfNeeded(BlinkGC::V8GCType gcType)
     }
 }
 
-void ThreadState::willStartV8GC()

[haraken, 2015/11/20 15:11:35]

And don't remove this code :) I'll prepare a CL to call this in a posted task.

-{
-    // Finish Oilpan's complete sweeping before running a V8 GC.
-    // This will let the GC collect more V8 objects.
-    //
-    // TODO(haraken): It's a bit too late for a major GC to schedule
-    // completeSweep() here, because gcPrologue for a major GC is called
-    // not at the point where the major GC started but at the point where
-    // the major GC requests object grouping.
-    completeSweep();
-
-    // The fact that the PageNavigation GC is scheduled means that there is
-    // a dead frame. In common cases, a sequence of Oilpan's GC => V8 GC =>
-    // Oilpan's GC is needed to collect the dead frame. So we force the
-    // PageNavigation GC before running the V8 GC.
-    if (gcState() == PageNavigationGCScheduled) {
-#if PRINT_HEAP_STATS
-        dataLogF("Scheduled PageNavigationGC\n");
-#endif
-        Heap::collectGarbage(BlinkGC::HeapPointersOnStack, BlinkGC::GCWithSweep, BlinkGC::PageNavigationGC);
-    }
-}
-
 void ThreadState::schedulePageNavigationGCIfNeeded(float estimatedRemovalRatio)
 {
     ASSERT(checkThread());