Do not crash if custom scrollbars have -webkit-appearane:searchfield-foo.

Source/core/rendering/RenderThemeChromiumMac.mm

Index: Source/core/rendering/RenderThemeChromiumMac.mm
diff --git a/Source/core/rendering/RenderThemeChromiumMac.mm b/Source/core/rendering/RenderThemeChromiumMac.mm
index dfdd539d4e613496131ddc2394af30b1696a6a86..2e163df0204f361514effb3fd4a3895058ec74f4 100644
--- a/Source/core/rendering/RenderThemeChromiumMac.mm
+++ b/Source/core/rendering/RenderThemeChromiumMac.mm
@@ -1663,6 +1663,8 @@ void RenderThemeChromiumMac::adjustSearchFieldStyle(RenderStyle* style, Element*
 
 bool RenderThemeChromiumMac::paintSearchFieldCancelButton(RenderObject* o, const PaintInfo& paintInfo, const IntRect& r)
 {
+    if (!o->node())
+        return false;
     Element* input = o->node()->shadowHost();
     if (!input)
         input = toElement(o->node());
@@ -1761,6 +1763,8 @@ void RenderThemeChromiumMac::adjustSearchFieldResultsDecorationStyle(RenderStyle
 
 bool RenderThemeChromiumMac::paintSearchFieldResultsDecoration(RenderObject* o, const PaintInfo& paintInfo, const IntRect& r)
 {
+    if (!o->node())
+        return false;
     Node* input = o->node()->shadowHost();
     if (!input)
         input = o->node();