macOS: Fix issue with display of auto-hide scrollbars

patch/patch.cfg

@@ -330,4 +330,10 @@ patches = [
     'name': 'webkit_scroll_mac_644144',
     'path': '../',
   },
+  {
+    # Fix issue with display of auto-hide scrollbars on macOS.
+    # https://bugs.chromium.org/p/chromium/issues/detail?id=688516#c6
+    'name': 'webkit_scroll_mac_688516',
+    'path': '../',
+  },
 ]

patch/patches/webkit_scroll_mac_688516.patch

@@ -0,0 +1,26 @@
+diff --git third_party/WebKit/Source/core/frame/FrameView.cpp third_party/WebKit/Source/core/frame/FrameView.cpp
+index 3ed16e5..3b2ce10 100644
+--- third_party/WebKit/Source/core/frame/FrameView.cpp
++++ third_party/WebKit/Source/core/frame/FrameView.cpp
+@@ -386,9 +386,9 @@ void FrameView::ScrollbarManager::setHasHorizontalScrollbar(bool hasScrollbar) {
+   if (hasScrollbar) {
+     m_hBar = createScrollbar(HorizontalScrollbar);
+     m_scrollableArea->layoutBox()->document().view()->addChild(m_hBar.get());
++    m_hBarIsAttached = 1;
+     m_scrollableArea->didAddScrollbar(*m_hBar, HorizontalScrollbar);
+     m_hBar->styleChanged();
+-    m_hBarIsAttached = 1;
+   } else {
+     m_hBarIsAttached = 0;
+     destroyScrollbar(HorizontalScrollbar);
+@@ -404,9 +404,9 @@ void FrameView::ScrollbarManager::setHasVerticalScrollbar(bool hasScrollbar) {
+   if (hasScrollbar) {
+     m_vBar = createScrollbar(VerticalScrollbar);
+     m_scrollableArea->layoutBox()->document().view()->addChild(m_vBar.get());
++    m_vBarIsAttached = 1;
+     m_scrollableArea->didAddScrollbar(*m_vBar, VerticalScrollbar);
+     m_vBar->styleChanged();
+-    m_vBarIsAttached = 1;
+   } else {
+     m_vBarIsAttached = 0;
+     destroyScrollbar(VerticalScrollbar);