Introduce toHTMLInputElement(Node*), and use it.

Source/core/rendering/HitTestResult.cpp

Index: Source/core/rendering/HitTestResult.cpp
diff --git a/Source/core/rendering/HitTestResult.cpp b/Source/core/rendering/HitTestResult.cpp
index 384e6ddb4c82bec90a37491eea82a6b5e0cb85e8..af9c7c551c5a183e199db49bc4f559836dd3bd71 100644
--- a/Source/core/rendering/HitTestResult.cpp
+++ b/Source/core/rendering/HitTestResult.cpp
@@ -245,7 +245,7 @@ String HitTestResult::altDisplayString() const
     }
     
     if (m_innerNonSharedNode->hasTagName(inputTag)) {
-        HTMLInputElement* input = static_cast<HTMLInputElement*>(m_innerNonSharedNode.get());
+        HTMLInputElement* input = toHTMLInputElement(m_innerNonSharedNode.get());
         return displayString(input->alt(), m_innerNonSharedNode.get());
     }
 
@@ -375,7 +375,7 @@ bool HitTestResult::isContentEditable() const
         return true;
 
     if (m_innerNonSharedNode->hasTagName(inputTag))
-        return static_cast<HTMLInputElement*>(m_innerNonSharedNode.get())->isTextField();
+        return toHTMLInputElement(m_innerNonSharedNode.get())->isTextField();
 
     return m_innerNonSharedNode->rendererIsEditable();
 }