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

Also add stuff to allow for Finch based control.

[email protected],[email protected],[email protected],[email protected]
BUG=490015

Review-Url: https://codereview.chromium.org/2184973002
Cr-Commit-Position: refs/heads/master@{#409713}
diff --git a/third_party/WebKit/LayoutTests/VirtualTestSuites b/third_party/WebKit/LayoutTests/VirtualTestSuites
index b846440..a73430f 100644
--- a/third_party/WebKit/LayoutTests/VirtualTestSuites
+++ b/third_party/WebKit/LayoutTests/VirtualTestSuites
@@ -69,6 +69,11 @@
   },
   {
     "prefix": "stable",
+    "base": "http/tests/navigation",
+    "args": ["--stable-release-mode"]
+  },
+  {
+    "prefix": "stable",
     "base": "animations-unprefixed",
     "args": ["--stable-release-mode"]
   },