Add null check to LayoutSliderContainer::HasVerticalAppearance

Bug: 769681
Change-Id: I28e9597aa2d1888f9890bb37d536b1e3b3886330
Reviewed-on: https://chromium-review.googlesource.com/692956Reviewed-by: Stefan Zager <szager@chromium.org>
Commit-Queue: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#505897}

third_party/WebKit/Source/core/layout/LayoutSliderContainer.cpp

@@ -53,8 +53,9 @@ inline static Decimal SliderPosition(HTMLInputElement* element) {
 
 inline static bool HasVerticalAppearance(HTMLInputElement* input) {
   DCHECK(input->GetLayoutObject());
+  if (!input->GetLayoutObject() || !input->GetLayoutObject()->Style())
+    return false;
   const ComputedStyle& slider_style = input->GetLayoutObject()->StyleRef();
-
   return slider_style.Appearance() == kSliderVerticalPart;
 }