Apply OwnPtr|PassOwnPtr to m_validationMessageClient and setValidationMessageClient() in Page class

Source/core/html/forms/ValidationMessage.cpp

Index: Source/core/html/forms/ValidationMessage.cpp
diff --git a/Source/core/html/forms/ValidationMessage.cpp b/Source/core/html/forms/ValidationMessage.cpp
index 57ee0eb6b8f37ecb778f1018bff07398770d4bd7..78046464722525708059d86d852328735944ea5b 100644
--- a/Source/core/html/forms/ValidationMessage.cpp
+++ b/Source/core/html/forms/ValidationMessage.cpp
@@ -60,9 +60,8 @@ ValidationMessageClient* ValidationMessage::validationMessageClient() const
     Page* page = m_element->document().page();
     if (!page)
         return 0;
-    // The form valdiation feature requires ValidationMessageClient.
-    ASSERT(page->validationMessageClient());
-    return page->validationMessageClient();
+
+    return &page->validationMessageClient();
 }
 
 void ValidationMessage::updateValidationMessage(const String& message)