Add HTTP-Bad Phase 3 experiment to field trial testing config

Some browser tests needed to be updated accordingly. I deleted a couple
that were redundant with tests where the field trial is enabled. For a
few others that only made sense in the pre-field trial world, I just
disabled the feature for them, though we'll want to clean them up
eventually after the field trial launches.

Bug: 807062
Change-Id: I480b2527375368d6146c1ddace2551dece9ec596
Reviewed-on: https://chromium-review.googlesource.com/891677Reviewed-by: Eric Lawrence <elawrence@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Commit-Queue: Emily Stark <estark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533845}

testing/variations/fieldtrial_testing_config.json

@@ -1596,6 +1596,29 @@
             ]
         }
     ],
+    "HTTPBadPhase3": [
+        {
+            "platforms": [
+                "android",
+                "chromeos",
+                "ios",
+                "linux",
+                "mac",
+                "win"
+            ],
+            "experiments": [
+                {
+                    "name": "NotSecureWarning",
+                    "params": {
+                        "treatment": "warning"
+                    },
+                    "enable_features": [
+                        "MarkHttpAs"
+                    ]
+                }
+            ]
+        }
+    ],
     "Html5ByDefault": [
         {
             "platforms": [