Oilpan: Correct static_asserts about VectorTraits::canInitializeWithMemset

Source/platform/heap/Heap.h

Index: Source/platform/heap/Heap.h
diff --git a/Source/platform/heap/Heap.h b/Source/platform/heap/Heap.h
index 629efc43eba2132accc62c286262c5c21599c549..146691916d522d2c1617d5c3409f139e38d20bc6 100644
--- a/Source/platform/heap/Heap.h
+++ b/Source/platform/heap/Heap.h
@@ -1922,12 +1922,7 @@ struct TraceInCollectionTrait<NoWeakHandlingInCollections, strongify, blink::Hea
     template<typename VisitorDispatcher>
     static bool trace(VisitorDispatcher visitor, void* self)
     {
-        // The allocator can oversize the allocation a little, according to
-        // the allocation granularity.  The extra size is included in the
-        // payloadSize call below, since there is nowhere to store the
-        // originally allocated memory.  This assert ensures that visiting the
-        // last bit of memory can't cause trouble.
-        static_assert(!ShouldBeTraced<Traits>::value || sizeof(T) > blink::allocationGranularity || Traits::canInitializeWithMemset, "heap overallocation can cause spurious visits");
+        static_assert(!ShouldBeTraced<Traits>::value || Traits::canInitializeWithMemset, "HeapVector doesn't support objects that cannot be initialized with memset.");
 
         T* array = reinterpret_cast<T*>(self);
         blink::HeapObjectHeader* header = blink::HeapObjectHeader::fromPayload(self);
@@ -2218,6 +2213,9 @@ struct TraceTrait<HeapHashTableBacking<Table>> {
 template<typename T, typename Traits>
 void HeapVectorBacking<T, Traits>::finalize(void* pointer)
 {
+    static_assert(Traits::needsDestruction, "HeapVectors that don't require destructors should not reach here.");

[sof, 2015/04/24 12:26:09]

"Only vector buffers with items requiring destruction should be finalized" ?
(i.e., deques are backed by same.)

+    static_assert(Traits::canInitializeWithMemset, "HeapVector doesn't support objects that cannot be initialized with memset.");
+
     ASSERT(!WTF::IsTriviallyDestructible<T>::value);
     HeapObjectHeader* header = HeapObjectHeader::fromPayload(pointer);
     // Use the payload size as recorded by the heap to determine how many