Flag to disable SMIL support

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 69 matching lines @@
     "prefix": "stable",
     "base": "fast/css3-text/css3-text-decoration/stable",
     "args": ["--stable-release-mode"]
   },
   {
     "prefix": "stable",
     "base": "web-animations-api",
     "args": ["--stable-release-mode"]
   },
   {
+    "prefix": "without-smil",
+    "base": "svg/animations/exposed",
+    "args": ["--disable-blink-features=smil"]
+  },
+  {
     "prefix": "linux-subpixel",
     "base": "platform/linux/fast/text/subpixel",
     "args": ["--enable-webkit-text-subpixel-positioning"]
   },
   {
     "prefix": "threaded",
     "base": "printing",
     "args": ["--enable-threaded-compositing"]
   },
   {
@@ skipping 36 matching lines @@
     "base": "media/mediasession",
     "args": ["--enable-blink-features=MediaSession"]
   },
   {
     "prefix": "sharedarraybuffer",
     "base": "fast/workers",
     "args": ["--js-flags=--harmony-sharedarraybuffer",
              "--enable-blink-features=SharedArrayBuffer"]
   }
 ]