blink: removes unused function from BoxVisualOverflowModel

BUG=none
TEST=none

Change-Id: I397656c55fe211615ae3d1d4cbc167cc2c1feee8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2396616Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804933}

third_party/blink/renderer/core/layout/overflow_model.h

@@ -202,10 +202,6 @@ class BoxVisualOverflowModel {
     self_visual_overflow_.Unite(rect);
   }
 
-  void ClearContentsVisualOverflow() {
-    contents_visual_overflow_ = LayoutRect();
-  }
-
   const LayoutRect& ContentsVisualOverflowRect() const {
     return contents_visual_overflow_;
   }