Refactor: Clear m_axObjectCache when AXObject detaches

Source/modules/accessibility/AXListBoxOption.cpp

Index: Source/modules/accessibility/AXListBoxOption.cpp
diff --git a/Source/modules/accessibility/AXListBoxOption.cpp b/Source/modules/accessibility/AXListBoxOption.cpp
index f1c1b919a4f4ab0314921ac8cd7aff54c1c36fa7..06e2c3c469e24e8572b0e73588f1a414d570d323 100644
--- a/Source/modules/accessibility/AXListBoxOption.cpp
+++ b/Source/modules/accessibility/AXListBoxOption.cpp
@@ -39,7 +39,7 @@ namespace blink {
 
 using namespace HTMLNames;
 
-AXListBoxOption::AXListBoxOption(LayoutObject* layoutObject, AXObjectCacheImpl* axObjectCache)
+AXListBoxOption::AXListBoxOption(LayoutObject* layoutObject, AXObjectCacheImpl& axObjectCache)
     : AXLayoutObject(layoutObject, axObjectCache)
 {
 }
@@ -48,7 +48,7 @@ AXListBoxOption::~AXListBoxOption()
 {
 }
 
-PassRefPtr<AXListBoxOption> AXListBoxOption::create(LayoutObject* layoutObject, AXObjectCacheImpl* axObjectCache)
+PassRefPtr<AXListBoxOption> AXListBoxOption::create(LayoutObject* layoutObject, AXObjectCacheImpl& axObjectCache)
 {
     return adoptRef(new AXListBoxOption(layoutObject, axObjectCache));
 }