[ResourceScheduler] Make throttling H2+QUIC default disabled

Since we don't know for sure what the outcome will be and need to perform
field trials, default to disabled.

BUG=655585

Review-Url: https://chromiumcodereview.appspot.com/2441633002
Cr-Commit-Position: refs/heads/master@{#426508}

content/browser/loader/resource_scheduler.cc

@@ -37,7 +37,7 @@ namespace {
 // HTTP/1.1 resources are. Disabling this appears to have negative performance
 // impact, see https://crbug.com/655585.
 const base::Feature kPrioritySupportedRequestsDelayable{
-    "PrioritySupportedRequestsDelayable", base::FEATURE_ENABLED_BY_DEFAULT};
+    "PrioritySupportedRequestsDelayable", base::FEATURE_DISABLED_BY_DEFAULT};
 
 enum StartMode {
   START_SYNC,

content/browser/loader/resource_scheduler_unittest.cc

@@ -344,6 +344,11 @@ TEST_F(ResourceSchedulerTest, OneLowLoadsUntilBodyInsertedExceptSpdy) {
 
 TEST_F(ResourceSchedulerTest,
        OneLowLoadsUntilBodyInsertedEvenSpdyWhenDelayable) {
+  base::test::ScopedFeatureList scoped_feature_list;
+  scoped_feature_list.InitFromCommandLine(kPrioritySupportedRequestsDelayable,
+                                          "");
+
+  InitializeScheduler();
   http_server_properties_.SetSupportsSpdy(
       url::SchemeHostPort("https", "spdyhost", 443), true);
   std::unique_ptr<TestRequest> high(
@@ -684,6 +689,11 @@ TEST_F(ResourceSchedulerTest, SpdyProxySchedulesImmediately) {
 }
 
 TEST_F(ResourceSchedulerTest, SpdyProxyDelayable) {
+  base::test::ScopedFeatureList scoped_feature_list;
+  scoped_feature_list.InitFromCommandLine(kPrioritySupportedRequestsDelayable,
+                                          "");
+  InitializeScheduler();
+
   std::unique_ptr<TestRequest> high(
       NewRequest("http://host/high", net::HIGHEST));
   std::unique_ptr<TestRequest> low(NewRequest("http://host/low", net::LOWEST));
@@ -741,6 +751,11 @@ TEST_F(ResourceSchedulerTest, NewSpdyHostInDelayableRequests) {
 }
 
 TEST_F(ResourceSchedulerTest, NewDelayableSpdyHostInDelayableRequests) {
+  base::test::ScopedFeatureList scoped_feature_list;
+  scoped_feature_list.InitFromCommandLine(kPrioritySupportedRequestsDelayable,
+                                          "");
+  InitializeScheduler();
+
   scheduler()->OnWillInsertBody(kChildId, kRouteId);
   const int kMaxNumDelayableRequestsPerClient = 10;  // Should match the .cc.
 

testing/variations/fieldtrial_testing_config.json

@@ -1386,6 +1386,25 @@
             ]
         }
     ],
+    "PrioritySupportedRequestsDelayableStudy": [
+        {
+            "platforms": [
+                "chromeos",
+                "linux",
+                "mac",
+                "win",
+                "android"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "PrioritySupportedRequestsDelayable"
+                    ]
+                }
+            ]
+        }
+    ],
     "ProgressBarAnimationAndroid": [
         {
             "platforms": [