Enable new multicol for testing and experimental web platform features.

LayoutTests/VirtualTestSuites

 [
   {
     "prefix": "gpu",
     "base": "fast/canvas",
     "args": ["--enable-accelerated-2d-canvas",
              "--disable-display-list-2d-canvas"]
   },
   {
     "prefix": "gpu",
     "base": "canvas/philip",
@@ skipping 85 matching lines @@
              "--enable-fixed-layout", "--enable-viewport", "--disable-canvas-aa",
              "--disable-composited-antialiasing"]
   },
   {
     "prefix": "stable",
     "base": "fast/css3-text/css3-text-decoration/stable",
     "args": ["--stable-release-mode"]
   },
   {
     "prefix": "stable",
+    "base": "compositing/columns",
+    "args": ["--stable-release-mode"]
+  },
+  {
+    "prefix": "stable",
+    "base": "fast/multicol",
+    "args": ["--stable-release-mode"]
+  },
+  {
+    "prefix": "stable",
+    "base": "fast/pagination",
+    "args": ["--stable-release-mode"]
+  },
+  {
+    "prefix": "stable",
     "base": "web-animations-api",
     "args": ["--stable-release-mode"]
   },
   {
     "prefix": "linux-subpixel",
     "base": "platform/linux/fast/text/subpixel",
     "args": ["--enable-webkit-text-subpixel-positioning"]
   },
   {
     "prefix": "antialiasedtext",
     "base": "fast/text",
     "args": ["--enable-direct-write",
              "--enable-font-antialiasing"]
   },
   {
     "prefix": "threaded",
     "base": "printing",
     "args": ["--enable-threaded-compositing"]
   },
   {
-    "prefix": "regionbasedmulticol",
-    "base": "compositing/columns",
-    "args": ["--enable-region-based-columns"]
-  },
-  {
-    "prefix": "regionbasedmulticol",
-    "base": "fast/multicol",
-    "args": ["--enable-region-based-columns"]
-  },
-  {
-    "prefix": "regionbasedmulticol",
-    "base": "fast/pagination",
-    "args": ["--enable-region-based-columns"]
-  },
-  {
     "prefix": "slimmingpaint",
     "base": "fast/block",
     "args": ["--enable-slimming-paint"],
     "reference_args": []
   },
   {
     "prefix": "slimmingpaint",
     "base": "fast/frames",
     "args": ["--enable-slimming-paint"],
     "reference_args": []
@@ skipping 107 matching lines @@
   },
   {
     "prefix": "slimmingpaint",
     "base": "fast/css",
     "args": ["--enable-slimming-paint"],
     "reference_args": []
   },
   {
     "prefix": "slimmingpaint",
     "base": "fast/multicol",
-    "args": ["--enable-slimming-paint", "--enable-region-based-columns"],
-    "reference_args": ["--enable-region-based-columns"]
+    "args": ["--enable-slimming-paint"],
+    "reference_args": []
   },
   {
     "prefix": "rootlayerscrolls",
     "base": "fast/scrolling",
     "args": ["--root-layer-scrolls"]
   },
   {
     "prefix": "slimmingpaint",
     "base": "fast/canvas",
     "args": ["--enable-slimming-paint"],
@@ skipping 43 matching lines @@
     "prefix": "scroll_customization",
     "base": "fast/events/touch",
     "args": ["--enable-blink-features=ScrollCustomization"]
   },
   {
     "prefix": "smoothscrolling",
     "base": "fast/events/touch/gesture",
     "args": ["--enable-smooth-scrolling"]
   }
 ]