Add CSS2/normal-flow LayoutNG virtual test suite.

third_party/WebKit/LayoutTests/VirtualTestSuites

 [
   {
     "prefix": "color_space",
     "base": "fast/canvas/color-space",
     "args": ["--enable-color-correct-rendering",
              "--enable-true-color-rendering"]
   },
   {
     "prefix": "gpu",
     "base": "fast/canvas",
@@ skipping 435 matching lines @@
     "prefix": "layout_ng",
     "base": "fast/block/float",
     "args": ["--enable-blink-features=LayoutNG"]
   },
   {
     "prefix": "layout_ng",
     "base": "external/wpt/css/CSS2/linebox",
     "args": ["--enable-blink-features=LayoutNG"]
   },
   {
+    "prefix": "layout_ng",
+    "base": "external/wpt/css/CSS2/normal-flow",
+    "args": ["--enable-blink-features=LayoutNG"]
+  },
+  {
     "prefix": "feature-policy",
     "base": "http/tests/feature-policy",
     "args": ["--enable-blink-features=FeaturePolicy"]
   },
   {
     "prefix": "mojo-localstorage",
     "base": "external/wpt/webstorage",
     "args": ["--mojo-local-storage"]
   },
   {
     "prefix": "mojo-localstorage",
     "base": "storage/domstorage/localstorage",
     "args": ["--mojo-local-storage"]
   },
   {
     "prefix": "print_browser",
     "base": "print_testharness",
     "args": ["--enable-print-browser"]
   },
   {
     "prefix": "experimental-canvas-features",
     "base": "fast/canvas-experimental",
     "args": ["--enable-experimental-canvas-features"]
   }
 ]