Introduce HTMLDataListOptionsCollection subclass for HTMLCollection

Source/core/rendering/RenderTheme.cpp

Index: Source/core/rendering/RenderTheme.cpp
diff --git a/Source/core/rendering/RenderTheme.cpp b/Source/core/rendering/RenderTheme.cpp
index a23981557e2f02461f5442a86c1f64212808b39c..98a26309a7a2522aa225c4ad352ef656bf28eace 100644
--- a/Source/core/rendering/RenderTheme.cpp
+++ b/Source/core/rendering/RenderTheme.cpp
@@ -32,6 +32,7 @@
 #include "core/frame/LocalFrame.h"
 #include "core/html/HTMLCollection.h"
 #include "core/html/HTMLDataListElement.h"
+#include "core/html/HTMLDataListOptionsCollection.h"
 #include "core/html/HTMLFormControlElement.h"
 #include "core/html/HTMLInputElement.h"
 #include "core/html/HTMLMeterElement.h"
@@ -877,13 +878,11 @@ void RenderTheme::paintSliderTicks(RenderObject* o, const PaintInfo& paintInfo,
         tickRegionSideMargin = trackBounds.y() + (thumbSize.width() - tickSize.width() * zoomFactor) / 2.0;
         tickRegionWidth = trackBounds.height() - thumbSize.width();
     }
-    RefPtrWillBeRawPtr<HTMLCollection> options = dataList->options();
+    RefPtrWillBeRawPtr<HTMLDataListOptionsCollection> options = dataList->options();
     GraphicsContextStateSaver stateSaver(*paintInfo.context);
     paintInfo.context->setFillColor(o->resolveColor(CSSPropertyColor));
-    for (unsigned i = 0; Element* element = options->item(i); i++) {
-        ASSERT(isHTMLOptionElement(*element));
-        HTMLOptionElement& optionElement = toHTMLOptionElement(*element);
-        String value = optionElement.value();
+    for (unsigned i = 0; HTMLOptionElement* optionElement = options->item(i); i++) {
+        String value = optionElement->value();
         if (!input->isValidValue(value))
             continue;
         double parsedValue = parseToDoubleForNumberType(input->sanitizeValue(value));