Remove now-unnecessary VectorTraits specializations.

Source/core/rendering/RenderGrid.cpp

Index: Source/core/rendering/RenderGrid.cpp
diff --git a/Source/core/rendering/RenderGrid.cpp b/Source/core/rendering/RenderGrid.cpp
index a459c51506629a0765ae64109fd4ab4de0e1b92e..3176096c22ee9f1ff4ed8027fda47a3300d56eca 100644
--- a/Source/core/rendering/RenderGrid.cpp
+++ b/Source/core/rendering/RenderGrid.cpp
@@ -33,7 +33,6 @@
 #include "core/rendering/style/GridCoordinate.h"
 #include "core/rendering/style/RenderStyle.h"
 #include "platform/LengthFunctions.h"
-#include "wtf/VectorTraits.h"
 
 namespace blink {
 
@@ -696,22 +695,6 @@ private:
     size_t m_span;
 };
 
-} // namespace blink
-
-namespace WTF  {
-
-template<>
-struct VectorTraits<blink::GridItemWithSpan> : SimpleClassVectorTraits<blink::GridItemWithSpan> {
-    // needsDestruction is by default defined in terms of IsPod<>, but as
-    // it doesn't handle embedded structs/enums (e.g., GridCoordinate),
-    // override it here.
-    static const bool needsDestruction = false;
-};
-
-} // namespace WTF
-
-namespace blink {
-
 void RenderGrid::resolveContentBasedTrackSizingFunctions(GridTrackSizingDirection direction, GridSizingData& sizingData, LayoutUnit& availableLogicalSpace)
 {
     sizingData.itemsSortedByIncreasingSpan.shrink(0);