Enable SpeculativePreconnect Field Trial Testing

This CL reenables SpeculativePreconnect field trial since the fix
https://crrev.com/c/778899 addressing performance regressions was
landed.

The predictors::kSpeculativePreconnectFeature is explicitly disabled in
net::Predictor browser tests because the LoadingPredictor if enabled
intercepts all prefetch and preconnect coming from a renderer.

Bug: 699080
Change-Id: Id5e4bb785943e1963f2a6a8802f738f491bb7544
Reviewed-on: https://chromium-review.googlesource.com/893459Reviewed-by: Helen Li <xunjieli@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Commit-Queue: Alexandr Ilin <alexilin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533238}

chrome/browser/net/OWNERS

 file://net/OWNERS
 
+per-file *predictor*=alexilin@chromium.org
 per-file disk_cache_dir_policy_handler*=atwilson@chromium.org
 
 # COMPONENT: Internals>Network

chrome/browser/net/predictor_browsertest.cc

@@ -23,12 +23,14 @@
 #include "base/single_thread_task_runner.h"
 #include "base/stl_util.h"
 #include "base/synchronization/lock.h"
+#include "base/test/scoped_feature_list.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/browsing_data/browsing_data_helper.h"
 #include "chrome/browser/browsing_data/chrome_browsing_data_remover_delegate.h"
 #include "chrome/browser/net/predictor.h"
+#include "chrome/browser/predictors/loading_predictor_config.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
@@ -514,6 +516,8 @@ class PredictorBrowserTest : public InProcessBrowserTest {
         Predictor::kMaxSpeculativeResolveQueueDelayMs + 300);
     rule_based_resolver_proc_->AddRuleWithLatency("delay.google.com",
                                                   "127.0.0.1", 1000 * 60);
+    scoped_feature_list_.InitAndDisableFeature(
+        predictors::kSpeculativePreconnectFeature);
   }
 
   ~PredictorBrowserTest() override {}
@@ -804,6 +808,8 @@ class PredictorBrowserTest : public InProcessBrowserTest {
     EXPECT_TRUE(result);
   }
 
+  base::test::ScopedFeatureList scoped_feature_list_;
+
   const GURL startup_url_;
   const GURL referring_url_;
   const GURL target_url_;

testing/variations/fieldtrial_testing_config.json

@@ -3564,6 +3564,27 @@
             ]
         }
     ],
+    "SpeculativePreconnectValidation": [
+        {
+            "platforms": [
+                "win",
+                "mac",
+                "linux",
+                "android"
+            ],
+            "experiments": [
+                {
+                    "name": "Preconnect2",
+                    "params": {
+                        "mode": "preconnect"
+                    },
+                    "enable_features": [
+                        "SpeculativePreconnect"
+                    ]
+                }
+            ]
+        }
+    ],
     "StabilityDebugging": [
         {
             "platforms": [