Disable collection backing reallocation during pre finalizer

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

Index: third_party/WebKit/Source/platform/heap/HeapTest.cpp
diff --git a/third_party/WebKit/Source/platform/heap/HeapTest.cpp b/third_party/WebKit/Source/platform/heap/HeapTest.cpp
index 37e9aaef365e79ab770e66f8da9db5098621eab5..1d9e62cb1162d22aed21f7cd5bd350ec8832414a 100644
--- a/third_party/WebKit/Source/platform/heap/HeapTest.cpp
+++ b/third_party/WebKit/Source/platform/heap/HeapTest.cpp
@@ -1499,6 +1499,48 @@ class PreFinalizationAllocator
   Persistent<IntWrapper>* wrapper_;
 };
 
+class PreFinalizerBackingReallocationForbiddenCheck
+    : public GarbageCollectedFinalized<
+          PreFinalizerBackingReallocationForbiddenCheck> {
+  USING_PRE_FINALIZER(PreFinalizerBackingReallocationForbiddenCheck, Dispose);
+
+ public:
+  PreFinalizerBackingReallocationForbiddenCheck() {
+    vector_.push_back(nullptr);
+    EXPECT_LT(0ul, vector_.Capacity());
+    for (int i = 1; i <= 32; ++i) {
+      map_.insert(i, nullptr);
+    }
+    EXPECT_LT(32ul, map_.Capacity());
+  }
+
+  void Dispose() {
+    vector_.Clear();
+    EXPECT_LT(0ul, vector_.Capacity());
+    for (int i = 1; i <= 32; ++i) {
+      map_.erase(i);
+    }
+    EXPECT_LT(32ul, map_.Capacity());
+    // Clearing is OK inside a pre finalizer.
+    map_.Clear();
+    EXPECT_EQ(0ul, map_.Capacity());
+  }
+
+  DEFINE_INLINE_TRACE() {
+    visitor->Trace(vector_);
+    visitor->Trace(map_);
+  }
+
+ private:
+  HeapVector<Member<IntWrapper>> vector_;
+  HeapHashMap<int, Member<IntWrapper>> map_;
+};
+
+TEST(HeapTest, BackingReallocationForbidden) {
+  new PreFinalizerBackingReallocationForbiddenCheck();
+  PreciselyCollectGarbage();
+}
+
 TEST(HeapTest, Transition) {
   {
     RefCountedAndGarbageCollected::destructor_calls_ = 0;