Simplify redundant member function call in SetSelectionStateIfNeeded

This patch removes a redundant class specifier |LayoutObject::| for
|SetSelectionState()| call in |SetSelectionStateIfNeeded()| because
it is non-virtual member function for improving code health.

Change-Id: I68b58d07c5452e36e05b1a20a3e5d20eeee90237
Reviewed-on: https://chromium-review.googlesource.com/903524Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Yoichi Osato <yoichio@chromium.org>
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534662}

third_party/WebKit/Source/core/editing/LayoutSelection.cpp

@@ -278,9 +278,7 @@ static void SetSelectionStateIfNeeded(LayoutObject* layout_object,
   DCHECK_NE(state, SelectionState::kNone) << layout_object;
   if (layout_object->GetSelectionState() == state)
     return;
-  // TODO(yoichio): Once we make LayoutObject::SetSelectionState() tribial, use
-  // it directly.
-  layout_object->LayoutObject::SetSelectionState(state);
+  layout_object->SetSelectionState(state);
 
   // Set containing block SelectionState kContain for CSS ::selection style.
   // See LayoutObject::InvalidatePaintForSelection().