Fix an issue that page is not scrollable after Resizing back and forth

for an ordinary page, Resize() is called before layout(). Resize will trigger ScrollingCoordinator::scrollableAreaScrollLayerDidChange() to get called, and layout() will call ScrollView::setScrollbarModes().

Since ScrollingCoordinator::scrollableAreaScrollLayerDidChange() is called before ScrollView::setScrollbarModes(), it may use soon-to-be-outdated ScrollBarMode to set WebLayer's scrollable attribute.
We need to update layer's scrollable attribute when ScrollView::setScrollbarModes() is called during layout()

BUG=322477

Review URL: https://codereview.chromium.org/104033006

git-svn-id: svn://svn.chromium.org/blink/trunk@163721 bbb929c8-8fbe-4397-9dbb-9b2b20218538