Oilpan: put ClientRect(List) on the heap.

Source/core/html/track/vtt/VTTRegion.cpp

Index: Source/core/html/track/vtt/VTTRegion.cpp
diff --git a/Source/core/html/track/vtt/VTTRegion.cpp b/Source/core/html/track/vtt/VTTRegion.cpp
index f702407911fc91e32f12b43123bcca741c339811..5c9e2c498c5a6c301a7e1a8df4a8a7277296788f 100644
--- a/Source/core/html/track/vtt/VTTRegion.cpp
+++ b/Source/core/html/track/vtt/VTTRegion.cpp
@@ -373,7 +373,7 @@ void VTTRegion::displayLastVTTCueBox()
 
     // Find first cue that is not entirely displayed and scroll it upwards.
     for (Element* child = ElementTraversal::firstChild(*m_cueContainer); child && !m_scrollTimer.isActive(); child = ElementTraversal::nextSibling(*child)) {
-        RefPtrWillBeRawPtr<ClientRect> clientRect = child->getBoundingClientRect();
+        ClientRect* clientRect = child->getBoundingClientRect();
         float childTop = clientRect->top();
         float childBottom = clientRect->bottom();