Refactor: Clear m_axObjectCache when AXObject detaches

Source/modules/accessibility/AXTableHeaderContainer.cpp

Index: Source/modules/accessibility/AXTableHeaderContainer.cpp
diff --git a/Source/modules/accessibility/AXTableHeaderContainer.cpp b/Source/modules/accessibility/AXTableHeaderContainer.cpp
index 95a352bb82f5f6c77bca6efa12f755fe943d6c6f..e4a6224a1ccb5c6c21e3ad2f076c0c8ca9647447 100644
--- a/Source/modules/accessibility/AXTableHeaderContainer.cpp
+++ b/Source/modules/accessibility/AXTableHeaderContainer.cpp
@@ -33,7 +33,7 @@
 
 namespace blink {
 
-AXTableHeaderContainer::AXTableHeaderContainer(AXObjectCacheImpl* axObjectCache)
+AXTableHeaderContainer::AXTableHeaderContainer(AXObjectCacheImpl& axObjectCache)
     : AXMockObject(axObjectCache)
 {
 }
@@ -42,7 +42,7 @@ AXTableHeaderContainer::~AXTableHeaderContainer()
 {
 }
 
-PassRefPtr<AXTableHeaderContainer> AXTableHeaderContainer::create(AXObjectCacheImpl* axObjectCache)
+PassRefPtr<AXTableHeaderContainer> AXTableHeaderContainer::create(AXObjectCacheImpl& axObjectCache)
 {
     return adoptRef(new AXTableHeaderContainer(axObjectCache));
 }