Re-Compute slow scroll region on frameview visibility change.

third_party/WebKit/LayoutTests/VirtualTestSuites

 [
   {
     "prefix": "gpu",
     "base": "fast/canvas",
     "args": ["--enable-accelerated-2d-canvas",
              "--disable-display-list-2d-canvas"]
   },
   {
     "prefix": "display_list_2d_canvas",
     "base": "fast/canvas",
@@ skipping 121 matching lines @@
     "base": "platform/linux/fast/text/subpixel",
     "args": ["--enable-webkit-text-subpixel-positioning"]
   },
   {
     "prefix": "threaded",
     "base": "printing",
     "args": ["--enable-threaded-compositing"]
   },
   {
     "prefix": "rootlayerscrolls",
+    "base": "scrollingcoordinator",
+    "args": ["--root-layer-scrolls"]
+  },
+  {
+    "prefix": "rootlayerscrolls",
     "base": "fast/scrolling",
     "args": ["--root-layer-scrolls"]
   },
   {
     "prefix": "rootlayerscrolls",
     "base": "fast/history/scroll-restoration",
     "args": ["--root-layer-scrolls"]
   },
   {
     "prefix": "rootlayerscrolls",
@@ skipping 146 matching lines @@
     "prefix": "layout_ng",
     "base": "fast/block/basic",
     "args": ["--enable-blink-features=LayoutNG"]
   },
   {
     "prefix": "layout_ng",
     "base": "fast/block/margin-collapse",
     "args": ["--enable-blink-features=LayoutNG"]
   }
 ]