[oilpan] Completely move HTMLFormControlElement's hierarchy to the managed heap

Source/core/accessibility/AccessibilitySlider.cpp

Index: Source/core/accessibility/AccessibilitySlider.cpp
diff --git a/Source/core/accessibility/AccessibilitySlider.cpp b/Source/core/accessibility/AccessibilitySlider.cpp
index f29104df6fb16f62a81aea0875504907369aaee2..c70cce0e05bef083eba0b2b1975582a2945795f1 100644
--- a/Source/core/accessibility/AccessibilitySlider.cpp
+++ b/Source/core/accessibility/AccessibilitySlider.cpp
@@ -127,7 +127,7 @@ float AccessibilitySlider::minValueForRange() const
 
 void AccessibilitySlider::setValue(const String& value)
 {
-    HTMLInputElement* input = element();
+    Handle<HTMLInputElement> input = element();
     
     if (input->value() == value)
         return;
@@ -138,9 +138,9 @@ void AccessibilitySlider::setValue(const String& value)
     input->dispatchFormControlChangeEvent();
 }
 
-HTMLInputElement* AccessibilitySlider::element() const
+Result<HTMLInputElement> AccessibilitySlider::element() const
 {
-    return static_cast<HTMLInputElement*>(m_renderer->node());
+    return Handle<HTMLInputElement>(static_cast<HTMLInputElement*>(m_renderer->node()));
 }