Enable the experiment to delay low priority requests on multiplexed connections

Enable the experiment to delay low priority requests on multiplexed connections.
net-dev thread: https://groups.google.com/a/chromium.org/forum/#!topic/net-dev/abRbGlGlNd0
loading-dev thread: https://groups.google.com/a/chromium.org/forum/#!topic/loading-dev/s22tVFiDru0
predictability-advice: http://shortn/_WJaP3jsRbk

Cq-Include-Trybots: luci.chromium.try:linux_mojo
Change-Id: I6141733ec7bfbd45c6b3c3d8ed98857104dee442
Bug: 836552
Reviewed-on: https://chromium-review.googlesource.com/c/1257677Reviewed-by: Matt Menke <mmenke@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#596129}

services/network/public/cpp/features.cc

@@ -40,7 +40,7 @@ const base::Feature kThrottleDelayable{"ThrottleDelayable",
 // ResourceScheduler just as HTTP/1.1 resources are. However, requests from such
 // servers are not subject to kMaxNumDelayableRequestsPerHostPerClient limit.
 const base::Feature kDelayRequestsOnMultiplexedConnections{
-    "DelayRequestsOnMultiplexedConnections", base::FEATURE_DISABLED_BY_DEFAULT};
+    "DelayRequestsOnMultiplexedConnections", base::FEATURE_ENABLED_BY_DEFAULT};
 
 }  // namespace features
 }  // namespace network

services/network/resource_scheduler_params_manager.cc

@@ -87,8 +87,10 @@ ResourceSchedulerParamsManager::
               features::kDelayRequestsOnMultiplexedConnections,
               "MaxEffectiveConnectionType"));
 
-  if (!max_effective_connection_type)
-    return result;
+  if (!max_effective_connection_type) {
+    // Use a default value if one is not set using field trial params.
+    max_effective_connection_type = net::EFFECTIVE_CONNECTION_TYPE_3G;
+  }
 
   for (int ect = net::EFFECTIVE_CONNECTION_TYPE_SLOW_2G;
        ect <= max_effective_connection_type.value(); ++ect) {

services/network/resource_scheduler_params_manager_unittest.cc

@@ -87,7 +87,6 @@ class ResourceSchedulerParamsManagerTest : public testing::Test {
     switch (effective_connection_type) {
       case net::EFFECTIVE_CONNECTION_TYPE_UNKNOWN:
       case net::EFFECTIVE_CONNECTION_TYPE_OFFLINE:
-      case net::EFFECTIVE_CONNECTION_TYPE_3G:
       case net::EFFECTIVE_CONNECTION_TYPE_4G:
         EXPECT_EQ(10u, resource_scheduler_params_manager
                            .GetParamsForEffectiveConnectionType(
@@ -102,7 +101,20 @@ class ResourceSchedulerParamsManagerTest : public testing::Test {
                 .GetParamsForEffectiveConnectionType(effective_connection_type)
                 .delay_requests_on_multiplexed_connections);
         return;
-
+      case net::EFFECTIVE_CONNECTION_TYPE_3G:
+        EXPECT_EQ(10u, resource_scheduler_params_manager
+                           .GetParamsForEffectiveConnectionType(
+                               effective_connection_type)
+                           .max_delayable_requests);
+        EXPECT_EQ(0.0, resource_scheduler_params_manager
+                           .GetParamsForEffectiveConnectionType(
+                               effective_connection_type)
+                           .non_delayable_weight);
+        EXPECT_TRUE(
+            resource_scheduler_params_manager
+                .GetParamsForEffectiveConnectionType(effective_connection_type)
+                .delay_requests_on_multiplexed_connections);
+        return;
       case net::EFFECTIVE_CONNECTION_TYPE_SLOW_2G:
       case net::EFFECTIVE_CONNECTION_TYPE_2G:
         EXPECT_EQ(8u, resource_scheduler_params_manager
@@ -113,7 +125,7 @@ class ResourceSchedulerParamsManagerTest : public testing::Test {
                            .GetParamsForEffectiveConnectionType(
                                effective_connection_type)
                            .non_delayable_weight);
-        EXPECT_FALSE(
+        EXPECT_TRUE(
             resource_scheduler_params_manager
                 .GetParamsForEffectiveConnectionType(effective_connection_type)
                 .delay_requests_on_multiplexed_connections);
@@ -184,6 +196,17 @@ TEST_F(ResourceSchedulerParamsManagerTest,
                       .GetParamsForEffectiveConnectionType(ect)
                       .delay_requests_on_multiplexed_connections);
 
+    } else if (effective_connection_type == net::EFFECTIVE_CONNECTION_TYPE_3G) {
+      EXPECT_EQ(10u, resource_scheduler_params_manager
+                         .GetParamsForEffectiveConnectionType(ect)
+                         .max_delayable_requests);
+      EXPECT_EQ(0.0, resource_scheduler_params_manager
+                         .GetParamsForEffectiveConnectionType(ect)
+                         .non_delayable_weight);
+      EXPECT_FALSE(resource_scheduler_params_manager
+                       .GetParamsForEffectiveConnectionType(ect)
+                       .delay_requests_on_multiplexed_connections);
+
     } else {
       VerifyDefaultParams(
           resource_scheduler_params_manager,