Add UMA to count the usage of sendBeacon with non-simple Content-Type

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 51 matching lines @@
     "base": "webexposed",
     "args": ["--stable-release-mode"]
   },
   {
     "prefix": "stable",
     "base": "http/tests/serviceworker/webexposed",
     "args": ["--stable-release-mode"]
   },
   {
     "prefix": "stable",
+    "base": "http/tests/navigation",
+    "args": ["--stable-release-mode"]
+  },
+  {
+    "prefix": "stable",
     "base": "animations-unprefixed",
     "args": ["--stable-release-mode"]
   },
   {
     "prefix": "stable",
     "base": "media/stable",
     "args": ["--stable-release-mode"]
   },
   {
     "prefix": "android",
@@ skipping 171 matching lines @@
     "prefix": "documentwriteevaluator",
     "base": "http/tests/preload/document-write",
     "args": ["--enable-blink-features=DocumentWriteEvaluator"]
   },
   {
     "prefix": "asyncawait",
     "base": "inspector/sources/debugger-async/async-await",
     "args": ["--js-flags=--harmony-async-await"]
   }
 ]