[reland] Change net's predictor_tab_helper to use the new content Navigation API

testing/variations/fieldtrial_testing_config_mac.json

 {
     "AutofillClassifier": [
         {
             "group_name": "Enabled"
         }
     ],
     "AutofillFieldMetadata": [
         {
             "group_name": "Enabled"
         }
@@ skipping 94 matching lines @@
     "PageRevisitInstrumentation": [
         {
             "group_name": "Enabled"
         }
     ],
     "PasswordBranding": [
         {
             "group_name": "SmartLockBrandingSavePromptOnly"
         }
     ],
+    "PreconnectMore": [
+        {
+            "enable_features": [
+                "PreconnectMore"
+            ],
+            "group_name": "Enabled"
+        },
+        {

[Charlie Harrison, 2016/04/08 14:54:38]

I'll remove "Default" from these as isherman@ mentioned FYI bots will run
default configs.

+            "group_name": "Default"
+        }
+    ],
     "QUIC": [
         {
             "group_name": "Enabled"
         }
     ],
     "RefreshTokenDeviceId": [
         {
             "group_name": "Enabled"
         }
     ],
@@ skipping 158 matching lines @@
     ],
     "use-new-media-cache": [
         {
             "enable_features": [
                 "use-new-media-cache"
             ],
             "group_name": "Enabled"
         }
     ]
 }