predictors: Put manifests for ResourcePrefetchPredictor behind a flag.

chrome/browser/predictors/resource_prefetch_common_unittest.cc

Index: chrome/browser/predictors/resource_prefetch_common_unittest.cc
diff --git a/chrome/browser/predictors/resource_prefetch_common_unittest.cc b/chrome/browser/predictors/resource_prefetch_common_unittest.cc
index f5f3fa6518e161b7f3306a7f8a7e6349f5100a08..33ebc5939e1c864035fae65599f94227a01e73aa 100644
--- a/chrome/browser/predictors/resource_prefetch_common_unittest.cc
+++ b/chrome/browser/predictors/resource_prefetch_common_unittest.cc
@@ -72,6 +72,7 @@ class ResourcePrefetchCommonTest : public testing::Test {
     EXPECT_FALSE(config.IsMoreResourcesEnabledForTest());
     EXPECT_FALSE(config.IsSmallDBEnabledForTest());
     EXPECT_FALSE(config.is_url_learning_enabled);
+    EXPECT_FALSE(config.is_manifests_enabled);
     EXPECT_GT(config.min_resource_hits_to_trigger_prefetch, 1U);
   }
 
@@ -148,6 +149,18 @@ TEST_F(ResourcePrefetchCommonTest, EnableUrlLearning) {
   EXPECT_TRUE(config.is_url_learning_enabled);
 }
 
+TEST_F(ResourcePrefetchCommonTest, EnableManifests) {
+  variations::testing::VariationParamsManager params_manager(
+      "dummy-trial",
+      {{kModeParamName, kLearningMode}, {kEnableManifestsParamName, "true"}},
+      {kSpeculativeResourcePrefetchingFeatureName});
+
+  ResourcePrefetchPredictorConfig config;
+  EXPECT_TRUE(IsSpeculativeResourcePrefetchingEnabled(profile_.get(), &config));
+  TestIsPrefetchLearning(config);
+  EXPECT_TRUE(config.is_manifests_enabled);
+}
+
 // Verifies whether prefetching is disabled according to the network type. But
 // learning should not be disabled by network.
 TEST_F(ResourcePrefetchCommonTest, RespectsNetworkSettings) {