Redirect handling in resource prefetch predictor

chrome/browser/predictors/resource_prefetch_predictor_unittest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/predictors/resource_prefetch_predictor.h"
 
 #include <iostream>
 #include <memory>
 
 #include "base/memory/ptr_util.h"
@@ skipping 18 matching lines @@
 
 using testing::ContainerEq;
 using testing::Pointee;
 using testing::SetArgPointee;
 using testing::StrictMock;
 
 namespace predictors {
 
 typedef ResourcePrefetchPredictor::URLRequestSummary URLRequestSummary;
 typedef ResourcePrefetchPredictorTables::ResourceRow ResourceRow;
-typedef std::vector<ResourceRow> ResourceRows;
+typedef ResourcePrefetchPredictorTables::RedirectRow RedirectRow;
 typedef ResourcePrefetchPredictorTables::PrefetchData PrefetchData;
 typedef ResourcePrefetchPredictorTables::PrefetchDataMap PrefetchDataMap;
+typedef ResourcePrefetchPredictorTables::RedirectData RedirectData;
+typedef ResourcePrefetchPredictorTables::RedirectDataMap RedirectDataMap;
 
 // For printing failures nicely.
 void PrintTo(const ResourceRow& row, ::std::ostream* os) {
   *os << "["
       << "," << row.resource_url << "," << row.resource_type << ","
       << row.number_of_hits << "," << row.number_of_misses << ","
       << row.consecutive_misses << "," << row.average_position << ","
       << row.score << "]";
 }
 
 void PrintTo(const PrefetchData& data, ::std::ostream* os) {
   *os << "[" << data.key_type << "," << data.primary_key
       << "," << data.last_visit.ToInternalValue() << "]\n";
-  for (ResourceRows::const_iterator it = data.resources.begin();
-       it != data.resources.end(); ++it) {
+  for (const ResourceRow& resource : data.resources) {
     *os << "\t\t";
-    PrintTo(*it, os);
+    PrintTo(resource, os);
     *os << "\n";
   }
 }
 
 scoped_refptr<net::HttpResponseHeaders> MakeResponseHeaders(
     const char* headers) {
   return make_scoped_refptr(new net::HttpResponseHeaders(
       net::HttpUtil::AssembleRawHeaders(headers, strlen(headers))));
 }
 
@@ skipping 72 matching lines @@
  private:
   net::HttpResponseInfo response_info_;
   std::string mime_type_;
 };
 
 class MockResourcePrefetchPredictorTables
     : public ResourcePrefetchPredictorTables {
  public:
   MockResourcePrefetchPredictorTables() { }
 
-  MOCK_METHOD2(GetAllData, void(PrefetchDataMap* url_data_map,
-                                PrefetchDataMap* host_data_map));
-  MOCK_METHOD2(UpdateData, void(const PrefetchData& url_data,
-                                const PrefetchData& host_data));
-  MOCK_METHOD2(DeleteData, void(const std::vector<std::string>& urls,
-                                const std::vector<std::string>& hosts));
-  MOCK_METHOD2(DeleteSingleDataPoint, void(const std::string& key,
-                                           PrefetchKeyType key_type));
+  MOCK_METHOD4(GetAllData,
+               void(PrefetchDataMap* url_data_map,
+                    PrefetchDataMap* host_data_map,
+                    RedirectDataMap* url_redirect_data_map,
+                    RedirectDataMap* host_redirect_data_map));
+  MOCK_METHOD4(UpdateData,
+               void(const PrefetchData& url_data,
+                    const PrefetchData& host_data,
+                    const RedirectData& url_redirect_data,
+                    const RedirectData& host_redirect_data));
+  MOCK_METHOD2(DeleteResourceData,
+               void(const std::vector<std::string>& urls,
+                    const std::vector<std::string>& hosts));
+  MOCK_METHOD2(DeleteSingleResourceDataPoint,
+               void(const std::string& key, PrefetchKeyType key_type));
+  MOCK_METHOD2(DeleteRedirectData,
+               void(const std::vector<std::string>& urls,
+                    const std::vector<std::string>& hosts));
+  MOCK_METHOD2(DeleteSingleRedirectDataPoint,
+               void(const std::string& key, PrefetchKeyType key_type));
   MOCK_METHOD0(DeleteAllData, void());
 
  protected:
   ~MockResourcePrefetchPredictorTables() { }
 };
 
 class ResourcePrefetchPredictorTest : public testing::Test {
  public:
   ResourcePrefetchPredictorTest();
   ~ResourcePrefetchPredictorTest() override;
@@ skipping 17 matching lines @@
 
   NavigationID CreateNavigationID(int process_id,
                                   int render_frame_id,
                                   const std::string& main_frame_url) {
     NavigationID navigation_id(process_id, render_frame_id,
                                GURL(main_frame_url));
     navigation_id.creation_time = base::TimeTicks::Now();
     return navigation_id;
   }
 
-  ResourcePrefetchPredictor::URLRequestSummary CreateURLRequestSummary(
+  URLRequestSummary CreateURLRequestSummary(
       int process_id,
       int render_frame_id,
       const std::string& main_frame_url,
-      const std::string& resource_url,
-      content::ResourceType resource_type,
-      net::RequestPriority priority,
-      const std::string& mime_type,
-      bool was_cached) {
-    ResourcePrefetchPredictor::URLRequestSummary summary;
+      const std::string& resource_url = std::string(),
+      content::ResourceType resource_type = content::RESOURCE_TYPE_MAIN_FRAME,
+      net::RequestPriority priority = net::MEDIUM,
+      const std::string& mime_type = std::string(),
+      bool was_cached = false) {
+    URLRequestSummary summary;
     summary.navigation_id = CreateNavigationID(process_id, render_frame_id,
                                                main_frame_url);
-    summary.resource_url = GURL(resource_url);
+    summary.resource_url =
+        resource_url.empty() ? GURL(main_frame_url) : GURL(resource_url);
     summary.resource_type = resource_type;
     summary.priority = priority;
     summary.mime_type = mime_type;
     summary.was_cached = was_cached;
     return summary;
   }
 
+  URLRequestSummary CreateRedirectRequestSummary(
+      int process_id,
+      int render_frame_id,
+      const std::string& main_frame_url,
+      const std::string& redirect_url) {
+    URLRequestSummary summary =
+        CreateURLRequestSummary(process_id, render_frame_id, main_frame_url);
+    summary.redirect_url = GURL(redirect_url);
+    return summary;
+  }
+
   std::unique_ptr<net::URLRequest> CreateURLRequest(
       const GURL& url,
       net::RequestPriority priority,
       content::ResourceType resource_type,
       int render_process_id,
       int render_frame_id,
       bool is_main_frame) {
     std::unique_ptr<net::URLRequest> request =
         url_request_context_.CreateRequest(url, priority,
                                            &url_request_delegate_);
@@ skipping 20 matching lines @@
         lhs.mime_type == rhs.mime_type &&
         lhs.was_cached == rhs.was_cached;
   }
 
   void ResetPredictor() {
     ResourcePrefetchPredictorConfig config;
     config.max_urls_to_track = 3;
     config.max_hosts_to_track = 2;
     config.min_url_visit_count = 2;
     config.max_resources_per_entry = 4;
+    config.max_redirects_per_entry = 3;
     config.max_consecutive_misses = 2;
 
     // TODO(shishir): Enable the prefetching mode in the tests.
     config.mode |= ResourcePrefetchPredictorConfig::URL_LEARNING;
     config.mode |= ResourcePrefetchPredictorConfig::HOST_LEARNING;
     predictor_.reset(new ResourcePrefetchPredictor(config, profile_.get()));
     predictor_->set_mock_tables(mock_tables_);
   }
 
   void InitializeSampleData();
 
   base::MessageLoop loop_;
   content::TestBrowserThread ui_thread_;
   content::TestBrowserThread db_thread_;
   std::unique_ptr<TestingProfile> profile_;
   net::TestURLRequestContext url_request_context_;
 
   std::unique_ptr<ResourcePrefetchPredictor> predictor_;
   scoped_refptr<StrictMock<MockResourcePrefetchPredictorTables> > mock_tables_;
 
   PrefetchDataMap test_url_data_;
   PrefetchDataMap test_host_data_;
+  RedirectDataMap test_url_redirect_data_;
+  RedirectDataMap test_host_redirect_data_;
   PrefetchData empty_url_data_;
   PrefetchData empty_host_data_;
+  RedirectData empty_url_redirect_data_;
+  RedirectData empty_host_redirect_data_;
 
   MockURLRequestJobFactory url_request_job_factory_;
   EmptyURLRequestDelegate url_request_delegate_;
 };
 
 ResourcePrefetchPredictorTest::ResourcePrefetchPredictorTest()
     : loop_(base::MessageLoop::TYPE_DEFAULT),
       ui_thread_(content::BrowserThread::UI, &loop_),
       db_thread_(content::BrowserThread::DB, &loop_),
       profile_(new TestingProfile()),
       mock_tables_(new StrictMock<MockResourcePrefetchPredictorTables>()),
       empty_url_data_(PREFETCH_KEY_TYPE_URL, std::string()),
-      empty_host_data_(PREFETCH_KEY_TYPE_HOST, std::string()) {}
+      empty_host_data_(PREFETCH_KEY_TYPE_HOST, std::string()),
+      empty_url_redirect_data_(PREFETCH_KEY_TYPE_URL, std::string()),
+      empty_host_redirect_data_(PREFETCH_KEY_TYPE_HOST, std::string()) {}
 
 ResourcePrefetchPredictorTest::~ResourcePrefetchPredictorTest() {
   profile_.reset(NULL);
   base::RunLoop().RunUntilIdle();
 }
 
 void ResourcePrefetchPredictorTest::SetUp() {
   InitializeSampleData();
 
   ASSERT_TRUE(profile_->CreateHistoryService(true, false));
   profile_->BlockUntilHistoryProcessesPendingRequests();
   EXPECT_TRUE(HistoryServiceFactory::GetForProfile(
       profile_.get(), ServiceAccessType::EXPLICIT_ACCESS));
   // Initialize the predictor with empty data.
   ResetPredictor();
   EXPECT_EQ(predictor_->initialization_state_,
             ResourcePrefetchPredictor::NOT_INITIALIZED);
   EXPECT_CALL(*mock_tables_.get(),
               GetAllData(Pointee(ContainerEq(PrefetchDataMap())),
-                         Pointee(ContainerEq(PrefetchDataMap()))));
+                         Pointee(ContainerEq(PrefetchDataMap())),
+                         Pointee(ContainerEq(RedirectDataMap())),
+                         Pointee(ContainerEq(RedirectDataMap()))));
   InitializePredictor();
   EXPECT_TRUE(predictor_->inflight_navigations_.empty());
   EXPECT_EQ(predictor_->initialization_state_,
             ResourcePrefetchPredictor::INITIALIZED);
 
   url_request_context_.set_job_factory(&url_request_job_factory_);
 }
 
 void ResourcePrefetchPredictorTest::TearDown() {
   predictor_.reset(NULL);
@@ skipping 64 matching lines @@
     PrefetchData yahoo(PREFETCH_KEY_TYPE_HOST, "www.yahoo.com");
     yahoo.last_visit = base::Time::FromInternalValue(5);
     yahoo.resources.push_back(ResourceRow("http://google.com/image.png",
                                           content::RESOURCE_TYPE_IMAGE, 20, 1,
                                           0, 10.0, net::MEDIUM, false, false));
 
     test_host_data_.clear();
     test_host_data_.insert(std::make_pair("www.facebook.com", facebook));
     test_host_data_.insert(std::make_pair("www.yahoo.com", yahoo));
   }
+
+  {  // Url redirect data.
+    RedirectData facebook(PREFETCH_KEY_TYPE_URL, "http://fb.com/google");
+    facebook.last_visit = base::Time::FromInternalValue(6);
+    facebook.redirects.push_back(
+        RedirectRow("https://facebook.com/google", 5, 1, 0));
+    facebook.redirects.push_back(
+        RedirectRow("https://facebook.com/login", 3, 5, 1));
+
+    RedirectData nytimes(PREFETCH_KEY_TYPE_URL, "http://nyt.com");
+    nytimes.last_visit = base::Time::FromInternalValue(7);
+    nytimes.redirects.push_back(RedirectRow("https://nytimes.com", 2, 0, 0));
+
+    RedirectData google(PREFETCH_KEY_TYPE_URL, "http://google.com");
+    google.last_visit = base::Time::FromInternalValue(8);
+    google.redirects.push_back(RedirectRow("https://google.com", 3, 0, 0));
+
+    test_url_redirect_data_.clear();
+    test_url_redirect_data_.insert(
+        std::make_pair(facebook.primary_key, facebook));
+    test_url_redirect_data_.insert(
+        std::make_pair(nytimes.primary_key, nytimes));
+    test_url_redirect_data_.insert(std::make_pair(google.primary_key, google));
+  }
+
+  {  // Host redirect data.
+    RedirectData bbc(PREFETCH_KEY_TYPE_HOST, "bbc.com");
+    bbc.last_visit = base::Time::FromInternalValue(9);
+    bbc.redirects.push_back(RedirectRow("www.bbc.com", 8, 4, 1));
+    bbc.redirects.push_back(RedirectRow("m.bbc.com", 5, 8, 0));
+    bbc.redirects.push_back(RedirectRow("bbc.co.uk", 1, 3, 0));
+
+    RedirectData microsoft(PREFETCH_KEY_TYPE_HOST, "microsoft.com");
+    microsoft.last_visit = base::Time::FromInternalValue(10);
+    microsoft.redirects.push_back(RedirectRow("www.microsoft.com", 10, 0, 0));
+
+    test_host_redirect_data_.clear();
+    test_host_redirect_data_.insert(std::make_pair(bbc.primary_key, bbc));
+    test_host_redirect_data_.insert(
+        std::make_pair(microsoft.primary_key, microsoft));
+  }
 }
 
 TEST_F(ResourcePrefetchPredictorTest, LazilyInitializeEmpty) {
   // Tests that the predictor initializes correctly without any data.
   EXPECT_TRUE(predictor_->url_table_cache_->empty());
   EXPECT_TRUE(predictor_->host_table_cache_->empty());
+  EXPECT_TRUE(predictor_->url_redirect_table_cache_->empty());
+  EXPECT_TRUE(predictor_->host_redirect_table_cache_->empty());
 }
 
 TEST_F(ResourcePrefetchPredictorTest, LazilyInitializeWithData) {
   // Tests that the history and the db tables data are loaded correctly.
   AddUrlToHistory("http://www.google.com/", 4);
   AddUrlToHistory("http://www.yahoo.com/", 2);
 
   EXPECT_CALL(*mock_tables_.get(),
               GetAllData(Pointee(ContainerEq(PrefetchDataMap())),
-                         Pointee(ContainerEq(PrefetchDataMap()))))
+                         Pointee(ContainerEq(PrefetchDataMap())),
+                         Pointee(ContainerEq(RedirectDataMap())),
+                         Pointee(ContainerEq(RedirectDataMap()))))
       .WillOnce(DoAll(SetArgPointee<0>(test_url_data_),
-                      SetArgPointee<1>(test_host_data_)));
+                      SetArgPointee<1>(test_host_data_),
+                      SetArgPointee<2>(test_url_redirect_data_),
+                      SetArgPointee<3>(test_host_redirect_data_)));
 
   ResetPredictor();
   InitializePredictor();
 
   // Test that the internal variables correctly initialized.
   EXPECT_EQ(predictor_->initialization_state_,
             ResourcePrefetchPredictor::INITIALIZED);
   EXPECT_TRUE(predictor_->inflight_navigations_.empty());
 
   EXPECT_EQ(test_url_data_, *predictor_->url_table_cache_);
   EXPECT_EQ(test_host_data_, *predictor_->host_table_cache_);
+  EXPECT_EQ(test_url_redirect_data_, *predictor_->url_redirect_table_cache_);
+  EXPECT_EQ(test_host_redirect_data_, *predictor_->host_redirect_table_cache_);
 }
 
 TEST_F(ResourcePrefetchPredictorTest, NavigationNotRecorded) {
   // Single navigation but history count is low, so should not record.
   AddUrlToHistory("http://www.google.com", 1);
 
-  URLRequestSummary main_frame = CreateURLRequestSummary(
-      1, 1, "http://www.google.com", "http://www.google.com",
-      content::RESOURCE_TYPE_MAIN_FRAME, net::MEDIUM, std::string(), false);
+  URLRequestSummary main_frame =
+      CreateURLRequestSummary(1, 1, "http://www.google.com");
   predictor_->RecordURLRequest(main_frame);
   EXPECT_EQ(1U, predictor_->inflight_navigations_.size());
 
+  URLRequestSummary main_frame_redirect = CreateRedirectRequestSummary(
+      1, 1, "http://www.google.com", "https://www.google.com");
+  predictor_->RecordURLRedirect(main_frame_redirect);
+  EXPECT_EQ(1U, predictor_->inflight_navigations_.size());
+  main_frame = CreateURLRequestSummary(1, 1, "https://www.google.com");
+
   // Now add a few subresources.
   URLRequestSummary resource1 = CreateURLRequestSummary(
-      1, 1, "http://www.google.com", "http://google.com/style1.css",
+      1, 1, "https://www.google.com", "https://google.com/style1.css",
       content::RESOURCE_TYPE_STYLESHEET, net::MEDIUM, "text/css", false);
   predictor_->RecordURLResponse(resource1);
   URLRequestSummary resource2 = CreateURLRequestSummary(
-      1, 1, "http://www.google.com", "http://google.com/script1.js",
+      1, 1, "https://www.google.com", "https://google.com/script1.js",
       content::RESOURCE_TYPE_SCRIPT, net::MEDIUM, "text/javascript", false);
   predictor_->RecordURLResponse(resource2);
   URLRequestSummary resource3 = CreateURLRequestSummary(
-      1, 1, "http://www.google.com", "http://google.com/script2.js",
+      1, 1, "https://www.google.com", "https://google.com/script2.js",
       content::RESOURCE_TYPE_SCRIPT, net::MEDIUM, "text/javascript", false);
   predictor_->RecordURLResponse(resource3);
 
   PrefetchData host_data(PREFETCH_KEY_TYPE_HOST, "www.google.com");
   host_data.resources.push_back(ResourceRow(
-      "http://google.com/style1.css", content::RESOURCE_TYPE_STYLESHEET, 1, 0,
+      "https://google.com/style1.css", content::RESOURCE_TYPE_STYLESHEET, 1, 0,
       0, 1.0, net::MEDIUM, false, false));
-  host_data.resources.push_back(ResourceRow("http://google.com/script1.js",
+  host_data.resources.push_back(ResourceRow("https://google.com/script1.js",
                                             content::RESOURCE_TYPE_SCRIPT, 1, 0,
                                             0, 2.0, net::MEDIUM, false, false));
-  host_data.resources.push_back(ResourceRow("http://google.com/script2.js",
+  host_data.resources.push_back(ResourceRow("https://google.com/script2.js",
                                             content::RESOURCE_TYPE_SCRIPT, 1, 0,
                                             0, 3.0, net::MEDIUM, false, false));
-  EXPECT_CALL(*mock_tables_.get(), UpdateData(empty_url_data_, host_data));
+  EXPECT_CALL(*mock_tables_.get(),
+              UpdateData(empty_url_data_, host_data, empty_url_redirect_data_,
+                         empty_host_redirect_data_));
 
-  predictor_->OnNavigationComplete(main_frame.navigation_id);
+  predictor_->RecordMainFrameLoadComplete(main_frame.navigation_id);
   profile_->BlockUntilHistoryProcessesPendingRequests();
 }
 
 TEST_F(ResourcePrefetchPredictorTest, NavigationUrlNotInDB) {
   // Single navigation that will be recorded. Will check for duplicate
   // resources and also for number of resources saved.
   AddUrlToHistory("http://www.google.com", 4);
 
-  URLRequestSummary main_frame = CreateURLRequestSummary(
-      1, 1, "http://www.google.com", "http://www.google.com",
-      content::RESOURCE_TYPE_MAIN_FRAME, net::MEDIUM, std::string(), false);
+  URLRequestSummary main_frame =
+      CreateURLRequestSummary(1, 1, "http://www.google.com");
   predictor_->RecordURLRequest(main_frame);
   EXPECT_EQ(1U, predictor_->inflight_navigations_.size());
 
   URLRequestSummary resource1 = CreateURLRequestSummary(
       1, 1, "http://www.google.com", "http://google.com/style1.css",
       content::RESOURCE_TYPE_STYLESHEET, net::MEDIUM, "text/css", false);
   predictor_->RecordURLResponse(resource1);
   URLRequestSummary resource2 = CreateURLRequestSummary(
       1, 1, "http://www.google.com", "http://google.com/script1.js",
       content::RESOURCE_TYPE_SCRIPT, net::MEDIUM, "text/javascript", false);
@@ skipping 25 matching lines @@
       0, 1.0, net::MEDIUM, false, false));
   url_data.resources.push_back(ResourceRow("http://google.com/script1.js",
                                            content::RESOURCE_TYPE_SCRIPT, 1, 0,
                                            0, 2.0, net::MEDIUM, false, false));
   url_data.resources.push_back(ResourceRow("http://google.com/script2.js",
                                            content::RESOURCE_TYPE_SCRIPT, 1, 0,
                                            0, 3.0, net::MEDIUM, false, false));
   url_data.resources.push_back(ResourceRow(
       "http://google.com/style2.css", content::RESOURCE_TYPE_STYLESHEET, 1, 0,
       0, 7.0, net::MEDIUM, false, false));
-  EXPECT_CALL(*mock_tables_.get(), UpdateData(url_data, empty_host_data_));
+  EXPECT_CALL(*mock_tables_.get(),
+              UpdateData(url_data, empty_host_data_, empty_url_redirect_data_,
+                         empty_host_redirect_data_));
 
   PrefetchData host_data(PREFETCH_KEY_TYPE_HOST, "www.google.com");
   host_data.resources = url_data.resources;
-  EXPECT_CALL(*mock_tables_.get(), UpdateData(empty_url_data_, host_data));
+  EXPECT_CALL(*mock_tables_.get(),
+              UpdateData(empty_url_data_, host_data, empty_url_redirect_data_,
+                         empty_host_redirect_data_));
 
   predictor_->OnNavigationComplete(main_frame.navigation_id);
   profile_->BlockUntilHistoryProcessesPendingRequests();
 }
 
 TEST_F(ResourcePrefetchPredictorTest, NavigationUrlInDB) {
   // Tests that navigation is recorded correctly for URL already present in
   // the database cache.
   AddUrlToHistory("http://www.google.com", 4);
 
   EXPECT_CALL(*mock_tables_.get(),
               GetAllData(Pointee(ContainerEq(PrefetchDataMap())),
-                         Pointee(ContainerEq(PrefetchDataMap()))))
+                         Pointee(ContainerEq(PrefetchDataMap())),
+                         Pointee(ContainerEq(RedirectDataMap())),
+                         Pointee(ContainerEq(RedirectDataMap()))))
       .WillOnce(DoAll(SetArgPointee<0>(test_url_data_),
                       SetArgPointee<1>(test_host_data_)));
   ResetPredictor();
   InitializePredictor();
   EXPECT_EQ(3U, predictor_->url_table_cache_->size());
   EXPECT_EQ(2U, predictor_->host_table_cache_->size());
 
   URLRequestSummary main_frame = CreateURLRequestSummary(
       1, 1, "http://www.google.com", "http://www.google.com",
       content::RESOURCE_TYPE_MAIN_FRAME, net::MEDIUM, std::string(), false);
@@ skipping 35 matching lines @@
       0, 1.0, net::MEDIUM, false, false));
   url_data.resources.push_back(ResourceRow("http://google.com/script1.js",
                                            content::RESOURCE_TYPE_SCRIPT, 1, 0,
                                            0, 2.0, net::MEDIUM, false, false));
   url_data.resources.push_back(ResourceRow("http://google.com/script4.js",
                                            content::RESOURCE_TYPE_SCRIPT, 11, 1,
                                            1, 2.1, net::MEDIUM, false, false));
   url_data.resources.push_back(ResourceRow("http://google.com/script2.js",
                                            content::RESOURCE_TYPE_SCRIPT, 1, 0,
                                            0, 3.0, net::MEDIUM, false, false));
-  EXPECT_CALL(*mock_tables_.get(), UpdateData(url_data, empty_host_data_));
+  EXPECT_CALL(*mock_tables_.get(),
+              UpdateData(url_data, empty_host_data_, empty_url_redirect_data_,
+                         empty_host_redirect_data_));
 
-  EXPECT_CALL(
-      *mock_tables_.get(),
-      DeleteSingleDataPoint("www.facebook.com", PREFETCH_KEY_TYPE_HOST));
+  EXPECT_CALL(*mock_tables_.get(),
+              DeleteSingleResourceDataPoint("www.facebook.com",
+                                            PREFETCH_KEY_TYPE_HOST));
 
   PrefetchData host_data(PREFETCH_KEY_TYPE_HOST, "www.google.com");
   host_data.resources.push_back(ResourceRow(
       "http://google.com/style1.css", content::RESOURCE_TYPE_STYLESHEET, 1, 0,
       0, 1.0, net::MEDIUM, false, false));
   host_data.resources.push_back(ResourceRow("http://google.com/script1.js",
                                             content::RESOURCE_TYPE_SCRIPT, 1, 0,
                                             0, 2.0, net::MEDIUM, false, false));
   host_data.resources.push_back(ResourceRow("http://google.com/script2.js",
                                             content::RESOURCE_TYPE_SCRIPT, 1, 0,
                                             0, 3.0, net::MEDIUM, false, false));
   host_data.resources.push_back(ResourceRow(
       "http://google.com/style2.css", content::RESOURCE_TYPE_STYLESHEET, 1, 0,
       0, 7.0, net::MEDIUM, false, false));
-  EXPECT_CALL(*mock_tables_.get(), UpdateData(empty_url_data_, host_data));
+  EXPECT_CALL(*mock_tables_.get(),
+              UpdateData(empty_url_data_, host_data, empty_url_redirect_data_,
+                         empty_host_redirect_data_));
 
   predictor_->OnNavigationComplete(main_frame.navigation_id);
   profile_->BlockUntilHistoryProcessesPendingRequests();
 }
 
 TEST_F(ResourcePrefetchPredictorTest, NavigationUrlNotInDBAndDBFull) {
   // Tests that a URL is deleted before another is added if the cache is full.
   AddUrlToHistory("http://www.nike.com/", 4);
 
   EXPECT_CALL(*mock_tables_.get(),
               GetAllData(Pointee(ContainerEq(PrefetchDataMap())),
-                         Pointee(ContainerEq(PrefetchDataMap()))))
+                         Pointee(ContainerEq(PrefetchDataMap())),
+                         Pointee(ContainerEq(RedirectDataMap())),
+                         Pointee(ContainerEq(RedirectDataMap()))))
       .WillOnce(DoAll(SetArgPointee<0>(test_url_data_),
                       SetArgPointee<1>(test_host_data_)));
   ResetPredictor();
   InitializePredictor();
   EXPECT_EQ(3U, predictor_->url_table_cache_->size());
   EXPECT_EQ(2U, predictor_->host_table_cache_->size());
 
   URLRequestSummary main_frame = CreateURLRequestSummary(
       1, 1, "http://www.nike.com", "http://www.nike.com",
       content::RESOURCE_TYPE_MAIN_FRAME, net::MEDIUM, std::string(), false);
   predictor_->RecordURLRequest(main_frame);
   EXPECT_EQ(1U, predictor_->inflight_navigations_.size());
 
   URLRequestSummary resource1 = CreateURLRequestSummary(
       1, 1, "http://www.nike.com", "http://nike.com/style1.css",
       content::RESOURCE_TYPE_STYLESHEET, net::MEDIUM, "text/css", false);
   predictor_->RecordURLResponse(resource1);
   URLRequestSummary resource2 = CreateURLRequestSummary(
       1, 1, "http://www.nike.com", "http://nike.com/image2.png",
       content::RESOURCE_TYPE_IMAGE, net::MEDIUM, "image/png", false);
   predictor_->RecordURLResponse(resource2);
 
-  EXPECT_CALL(
-      *mock_tables_.get(),
-      DeleteSingleDataPoint("http://www.google.com/", PREFETCH_KEY_TYPE_URL));
-  EXPECT_CALL(
-      *mock_tables_.get(),
-      DeleteSingleDataPoint("www.facebook.com", PREFETCH_KEY_TYPE_HOST));
+  EXPECT_CALL(*mock_tables_.get(),
+              DeleteSingleResourceDataPoint("http://www.google.com/",
+                                            PREFETCH_KEY_TYPE_URL));
+  EXPECT_CALL(*mock_tables_.get(),
+              DeleteSingleResourceDataPoint("www.facebook.com",
+                                            PREFETCH_KEY_TYPE_HOST));
 
   PrefetchData url_data(PREFETCH_KEY_TYPE_URL, "http://www.nike.com/");
   url_data.resources.push_back(ResourceRow(
       "http://nike.com/style1.css", content::RESOURCE_TYPE_STYLESHEET, 1, 0, 0,
       1.0, net::MEDIUM, false, false));
   url_data.resources.push_back(ResourceRow("http://nike.com/image2.png",
                                            content::RESOURCE_TYPE_IMAGE, 1, 0,
                                            0, 2.0, net::MEDIUM, false, false));
-  EXPECT_CALL(*mock_tables_.get(), UpdateData(url_data, empty_host_data_));
+  EXPECT_CALL(*mock_tables_.get(),
+              UpdateData(url_data, empty_host_data_, empty_url_redirect_data_,
+                         empty_host_redirect_data_));
 
   PrefetchData host_data(PREFETCH_KEY_TYPE_HOST, "www.nike.com");
   host_data.resources = url_data.resources;
-  EXPECT_CALL(*mock_tables_.get(), UpdateData(empty_url_data_, host_data));
+  EXPECT_CALL(*mock_tables_.get(),
+              UpdateData(empty_url_data_, host_data, empty_url_redirect_data_,
+                         empty_host_redirect_data_));
 
   predictor_->OnNavigationComplete(main_frame.navigation_id);
   profile_->BlockUntilHistoryProcessesPendingRequests();
 }
 
+TEST_F(ResourcePrefetchPredictorTest, RedirectUrlNotInDB) {
+  AddUrlToHistory("https://facebook.com/google", 4);
+
+  URLRequestSummary fb1 = CreateURLRequestSummary(1, 1, "http://fb.com/google");
+  predictor_->RecordURLRequest(fb1);
+  EXPECT_EQ(1U, predictor_->inflight_navigations_.size());
+
+  URLRequestSummary fb2 = CreateRedirectRequestSummary(
+      1, 1, "http://fb.com/google", "http://facebook.com/google");
+  predictor_->RecordURLRedirect(fb2);
+  URLRequestSummary fb3 = CreateRedirectRequestSummary(
+      1, 1, "http://facebook.com/google", "https://facebook.com/google");
+  predictor_->RecordURLRedirect(fb3);
+  NavigationID fb_end = CreateNavigationID(1, 1, "https://facebook.com/google");
+
+  // Since the navigation hasn't resources, corresponding entry
+  // in resource table will be deleted
+  EXPECT_CALL(*mock_tables_.get(),
+              DeleteSingleResourceDataPoint("https://facebook.com/google",
+                                            PREFETCH_KEY_TYPE_URL));
+  EXPECT_CALL(*mock_tables_.get(), DeleteSingleResourceDataPoint(
+                                       "facebook.com", PREFETCH_KEY_TYPE_HOST));
+
+  RedirectData url_redirect_data(PREFETCH_KEY_TYPE_URL, "http://fb.com/google");
+  url_redirect_data.redirects.push_back(
+      RedirectRow("https://facebook.com/google", 1, 0, 0));
+  EXPECT_CALL(*mock_tables_.get(),
+              UpdateData(empty_url_data_, empty_host_data_, url_redirect_data,
+                         empty_host_redirect_data_));
+
+  RedirectData host_redirect_data(PREFETCH_KEY_TYPE_HOST, "fb.com");
+  host_redirect_data.redirects.push_back(RedirectRow("facebook.com", 1, 0, 0));
+  EXPECT_CALL(*mock_tables_.get(),
+              UpdateData(empty_url_data_, empty_host_data_,
+                         empty_url_redirect_data_, host_redirect_data));
+
+  predictor_->RecordMainFrameLoadComplete(fb_end);
+  profile_->BlockUntilHistoryProcessesPendingRequests();
+}
+
+TEST_F(ResourcePrefetchPredictorTest, RedirectUrlInDB) {
+  // Tests that redirect is recorded correctly for URL already present in
+  // the database cache.
+  AddUrlToHistory("https://facebook.com/google", 4);
+
+  EXPECT_CALL(*mock_tables_.get(),
+              GetAllData(Pointee(ContainerEq(PrefetchDataMap())),
+                         Pointee(ContainerEq(PrefetchDataMap())),
+                         Pointee(ContainerEq(RedirectDataMap())),
+                         Pointee(ContainerEq(RedirectDataMap()))))
+      .WillOnce(DoAll(SetArgPointee<2>(test_url_redirect_data_),
+                      SetArgPointee<3>(test_host_redirect_data_)));
+  ResetPredictor();
+  InitializePredictor();
+  EXPECT_EQ(3U, predictor_->url_redirect_table_cache_->size());
+  EXPECT_EQ(2U, predictor_->host_redirect_table_cache_->size());
+
+  URLRequestSummary fb1 = CreateURLRequestSummary(1, 1, "http://fb.com/google");
+  predictor_->RecordURLRequest(fb1);
+  EXPECT_EQ(1U, predictor_->inflight_navigations_.size());
+
+  URLRequestSummary fb2 = CreateRedirectRequestSummary(
+      1, 1, "http://fb.com/google", "http://facebook.com/google");
+  predictor_->RecordURLRedirect(fb2);
+  URLRequestSummary fb3 = CreateRedirectRequestSummary(
+      1, 1, "http://facebook.com/google", "https://facebook.com/google");
+  predictor_->RecordURLRedirect(fb3);
+  NavigationID fb_end = CreateNavigationID(1, 1, "https://facebook.com/google");
+
+  // Oldest entries in tables will be superseded and deleted
+  EXPECT_CALL(*mock_tables_.get(),
+              DeleteSingleRedirectDataPoint("bbc.com", PREFETCH_KEY_TYPE_HOST));
+
+  // Since the navigation hasn't resources, corresponding entry
+  // in resource table will be deleted
+  EXPECT_CALL(*mock_tables_.get(),
+              DeleteSingleResourceDataPoint("https://facebook.com/google",
+                                            PREFETCH_KEY_TYPE_URL));
+  EXPECT_CALL(*mock_tables_.get(), DeleteSingleResourceDataPoint(
+                                       "facebook.com", PREFETCH_KEY_TYPE_HOST));
+
+  RedirectData url_redirect_data(PREFETCH_KEY_TYPE_URL, "http://fb.com/google");
+  url_redirect_data.redirects.push_back(
+      RedirectRow("https://facebook.com/google", 6, 1, 0));
+  // Exising redirect to https://facebook.com/login will be deleted because of
+  // too many consecutive misses.
+  EXPECT_CALL(*mock_tables_.get(),
+              UpdateData(empty_url_data_, empty_host_data_, url_redirect_data,
+                         empty_host_redirect_data_));
+
+  RedirectData host_redirect_data(PREFETCH_KEY_TYPE_HOST, "fb.com");
+  host_redirect_data.redirects.push_back(RedirectRow("facebook.com", 1, 0, 0));
+  EXPECT_CALL(*mock_tables_.get(),
+              UpdateData(empty_url_data_, empty_host_data_,
+                         empty_url_redirect_data_, host_redirect_data));
+
+  predictor_->RecordMainFrameLoadComplete(fb_end);
+  profile_->BlockUntilHistoryProcessesPendingRequests();
+}
+
 TEST_F(ResourcePrefetchPredictorTest, DeleteUrls) {
   // Add some dummy entries to cache.
   predictor_->url_table_cache_->insert(std::make_pair(
       "http://www.google.com/page1.html",
       PrefetchData(PREFETCH_KEY_TYPE_URL, "http://www.google.com/page1.html")));
   predictor_->url_table_cache_->insert(std::make_pair(
       "http://www.google.com/page2.html",
       PrefetchData(PREFETCH_KEY_TYPE_URL, "http://www.google.com/page2.html")));
   predictor_->url_table_cache_->insert(std::make_pair(
       "http://www.yahoo.com/",
@@ skipping 20 matching lines @@
   rows.push_back(history::URLRow(GURL("http://www.apple.com")));
   rows.push_back(history::URLRow(GURL("http://www.nike.com")));
 
   std::vector<std::string> urls_to_delete, hosts_to_delete;
   urls_to_delete.push_back("http://www.google.com/page2.html");
   urls_to_delete.push_back("http://www.apple.com/");
   urls_to_delete.push_back("http://www.nike.com/");
   hosts_to_delete.push_back("www.google.com");
   hosts_to_delete.push_back("www.apple.com");
 
-  EXPECT_CALL(
-      *mock_tables_.get(),
-      DeleteData(ContainerEq(urls_to_delete), ContainerEq(hosts_to_delete)));
+  EXPECT_CALL(*mock_tables_.get(),
+              DeleteResourceData(ContainerEq(urls_to_delete),
+                                 ContainerEq(hosts_to_delete)));
 
   predictor_->DeleteUrls(rows);
   EXPECT_EQ(2U, predictor_->url_table_cache_->size());
   EXPECT_EQ(1U, predictor_->host_table_cache_->size());
 
   EXPECT_CALL(*mock_tables_.get(), DeleteAllData());
 
   predictor_->DeleteAllUrls();
   EXPECT_TRUE(predictor_->url_table_cache_->empty());
   EXPECT_TRUE(predictor_->host_table_cache_->empty());
@@ skipping 10 matching lines @@
       2, 1, "http://www.yahoo.com", "http://www.yahoo.com",
       content::RESOURCE_TYPE_MAIN_FRAME, net::MEDIUM, std::string(), false);
 
   predictor_->OnMainFrameRequest(summary1);
   EXPECT_EQ(1U, predictor_->inflight_navigations_.size());
   predictor_->OnMainFrameRequest(summary2);
   EXPECT_EQ(2U, predictor_->inflight_navigations_.size());
   predictor_->OnMainFrameRequest(summary3);
   EXPECT_EQ(3U, predictor_->inflight_navigations_.size());
 
-  // Insert anther with same navigation id. It should replace.
+  // Insert another with same navigation id. It should replace.
   URLRequestSummary summary4 = CreateURLRequestSummary(
       1, 1, "http://www.nike.com", "http://www.nike.com",
       content::RESOURCE_TYPE_MAIN_FRAME, net::MEDIUM, std::string(), false);
   URLRequestSummary summary5 = CreateURLRequestSummary(
       1, 2, "http://www.google.com", "http://www.google.com",
       content::RESOURCE_TYPE_MAIN_FRAME, net::MEDIUM, std::string(), false);
 
   predictor_->OnMainFrameRequest(summary4);
   EXPECT_EQ(3U, predictor_->inflight_navigations_.size());
 
@@ skipping 11 matching lines @@
 
   EXPECT_TRUE(predictor_->inflight_navigations_.find(summary3.navigation_id) !=
               predictor_->inflight_navigations_.end());
   EXPECT_TRUE(predictor_->inflight_navigations_.find(summary4.navigation_id) !=
               predictor_->inflight_navigations_.end());
   EXPECT_TRUE(predictor_->inflight_navigations_.find(summary6.navigation_id) !=
               predictor_->inflight_navigations_.end());
 }
 
 TEST_F(ResourcePrefetchPredictorTest, OnMainFrameRedirect) {
-  URLRequestSummary summary1 = CreateURLRequestSummary(
-      1, 1, "http://www.google.com", "http://www.google.com",
-      content::RESOURCE_TYPE_MAIN_FRAME, net::MEDIUM, std::string(), false);
-  URLRequestSummary summary2 = CreateURLRequestSummary(
-      1, 2, "http://www.google.com", "http://www.google.com",
-      content::RESOURCE_TYPE_MAIN_FRAME, net::MEDIUM, std::string(), false);
-  URLRequestSummary summary3 = CreateURLRequestSummary(
-      2, 1, "http://www.yahoo.com", "http://www.yahoo.com",
-      content::RESOURCE_TYPE_MAIN_FRAME, net::MEDIUM, std::string(), false);
+  URLRequestSummary yahoo = CreateURLRequestSummary(1, 1, "http://yahoo.com");
 
-  predictor_->OnMainFrameRedirect(summary1);
+  URLRequestSummary bbc1 = CreateURLRequestSummary(2, 2, "http://bbc.com");
+  URLRequestSummary bbc2 = CreateRedirectRequestSummary(2, 2, "http://bbc.com",
+                                                        "https://www.bbc.com");
+  NavigationID bbc_end = CreateNavigationID(2, 2, "https://www.bbc.com");
+
+  URLRequestSummary youtube1 =
+      CreateURLRequestSummary(1, 2, "http://youtube.com");
+  URLRequestSummary youtube2 = CreateRedirectRequestSummary(
+      1, 2, "http://youtube.com", "https://youtube.com");
+  NavigationID youtube_end = CreateNavigationID(1, 2, "https://youtube.com");
+
+  URLRequestSummary nyt1 = CreateURLRequestSummary(2, 1, "http://nyt.com");
+  URLRequestSummary nyt2 = CreateRedirectRequestSummary(2, 1, "http://nyt.com",
+                                                        "http://nytimes.com");
+  URLRequestSummary nyt3 = CreateRedirectRequestSummary(
+      2, 1, "http://nytimes.com", "http://m.nytimes.com");
+  NavigationID nyt_end = CreateNavigationID(2, 1, "http://m.nytimes.com");
+
+  URLRequestSummary fb1 = CreateURLRequestSummary(1, 3, "http://fb.com");
+  URLRequestSummary fb2 = CreateRedirectRequestSummary(1, 3, "http://fb.com",
+                                                       "http://facebook.com");
+  URLRequestSummary fb3 = CreateRedirectRequestSummary(
+      1, 3, "http://facebook.com", "https://facebook.com");
+  URLRequestSummary fb4 = CreateRedirectRequestSummary(
+      1, 3, "https://facebook.com",
+      "https://m.facebook.com/?refsrc=https%3A%2F%2Fwww.facebook.com%2F&_rdr");
+  NavigationID fb_end = CreateNavigationID(
+      1, 3,
+      "https://m.facebook.com/?refsrc=https%3A%2F%2Fwww.facebook.com%2F&_rdr");
+
+  // Redirect with empty redirect_url will be deleted
+  predictor_->OnMainFrameRequest(yahoo);
+  EXPECT_EQ(1U, predictor_->inflight_navigations_.size());
+  predictor_->OnMainFrameRedirect(yahoo);
   EXPECT_TRUE(predictor_->inflight_navigations_.empty());
 
-  predictor_->OnMainFrameRequest(summary1);
+  // Redirect without previous request works fine
+  // predictor_->OnMainFrameRequest(bbc1) missing
+  predictor_->OnMainFrameRedirect(bbc2);
   EXPECT_EQ(1U, predictor_->inflight_navigations_.size());
-  predictor_->OnMainFrameRequest(summary2);
+  EXPECT_EQ(bbc1.navigation_id.main_frame_url,
+            predictor_->inflight_navigations_[bbc_end]->initial_url);
+
+  // http://youtube.com -> https://youtube.com
+  predictor_->OnMainFrameRequest(youtube1);
   EXPECT_EQ(2U, predictor_->inflight_navigations_.size());
+  predictor_->OnMainFrameRedirect(youtube2);
+  EXPECT_EQ(2U, predictor_->inflight_navigations_.size());
+  EXPECT_EQ(youtube1.navigation_id.main_frame_url,
+            predictor_->inflight_navigations_[youtube_end]->initial_url);
 
-  predictor_->OnMainFrameRedirect(summary3);
-  EXPECT_EQ(2U, predictor_->inflight_navigations_.size());
-  predictor_->OnMainFrameRedirect(summary1);
-  EXPECT_EQ(1U, predictor_->inflight_navigations_.size());
-  predictor_->OnMainFrameRedirect(summary2);
-  EXPECT_TRUE(predictor_->inflight_navigations_.empty());
+  // http://nyt.com -> http://nytimes.com -> http://m.nytimes.com
+  predictor_->OnMainFrameRequest(nyt1);
+  EXPECT_EQ(3U, predictor_->inflight_navigations_.size());
+  predictor_->OnMainFrameRedirect(nyt2);
+  predictor_->OnMainFrameRedirect(nyt3);
+  EXPECT_EQ(3U, predictor_->inflight_navigations_.size());
+  EXPECT_EQ(nyt1.navigation_id.main_frame_url,
+            predictor_->inflight_navigations_[nyt_end]->initial_url);
+
+  // http://fb.com -> http://facebook.com -> https://facebook.com ->
+  // https://m.facebook.com/?refsrc=https%3A%2F%2Fwww.facebook.com%2F&_rdr
+  predictor_->OnMainFrameRequest(fb1);
+  EXPECT_EQ(4U, predictor_->inflight_navigations_.size());
+  predictor_->OnMainFrameRedirect(fb2);
+  predictor_->OnMainFrameRedirect(fb3);
+  predictor_->OnMainFrameRedirect(fb4);
+  EXPECT_EQ(4U, predictor_->inflight_navigations_.size());
+  EXPECT_EQ(fb1.navigation_id.main_frame_url,
+            predictor_->inflight_navigations_[fb_end]->initial_url);
 }
 
 TEST_F(ResourcePrefetchPredictorTest, OnSubresourceResponse) {
   // If there is no inflight navigation, nothing happens.
   URLRequestSummary resource1 = CreateURLRequestSummary(
       1, 1, "http://www.google.com", "http://google.com/style1.css",
       content::RESOURCE_TYPE_STYLESHEET, net::MEDIUM, "text/css", false);
   predictor_->OnSubresourceResponse(resource1);
   EXPECT_TRUE(predictor_->inflight_navigations_.empty());
 
   // Add an inflight navigation.
   URLRequestSummary main_frame1 = CreateURLRequestSummary(
       1, 1, "http://www.google.com", "http://www.google.com",
       content::RESOURCE_TYPE_MAIN_FRAME, net::MEDIUM, std::string(), false);
   predictor_->OnMainFrameRequest(main_frame1);
   EXPECT_EQ(1U, predictor_->inflight_navigations_.size());
 
   // Now add a few subresources.
   URLRequestSummary resource2 = CreateURLRequestSummary(
       1, 1, "http://www.google.com", "http://google.com/script1.js",
       content::RESOURCE_TYPE_SCRIPT, net::MEDIUM, "text/javascript", false);
   URLRequestSummary resource3 = CreateURLRequestSummary(
       1, 1, "http://www.google.com", "http://google.com/script2.js",
       content::RESOURCE_TYPE_SCRIPT, net::MEDIUM, "text/javascript", false);
   predictor_->OnSubresourceResponse(resource1);
   predictor_->OnSubresourceResponse(resource2);
   predictor_->OnSubresourceResponse(resource3);
 
   EXPECT_EQ(1U, predictor_->inflight_navigations_.size());
-  EXPECT_EQ(3U,
-      predictor_->inflight_navigations_[main_frame1.navigation_id]->size());
+  EXPECT_EQ(3U, predictor_->inflight_navigations_[main_frame1.navigation_id]
+                    ->requests.size());
   EXPECT_TRUE(URLRequestSummaryAreEqual(
-      resource1,
-      predictor_->inflight_navigations_[main_frame1.navigation_id]->at(0)));
+      resource1, predictor_->inflight_navigations_[main_frame1.navigation_id]
+                     ->requests[0]));
   EXPECT_TRUE(URLRequestSummaryAreEqual(
-      resource2,
-      predictor_->inflight_navigations_[main_frame1.navigation_id]->at(1)));
+      resource2, predictor_->inflight_navigations_[main_frame1.navigation_id]
+                     ->requests[1]));
   EXPECT_TRUE(URLRequestSummaryAreEqual(
-      resource3,
-      predictor_->inflight_navigations_[main_frame1.navigation_id]->at(2)));
+      resource3, predictor_->inflight_navigations_[main_frame1.navigation_id]
+                     ->requests[2]));
 }
 
 TEST_F(ResourcePrefetchPredictorTest, HandledResourceTypes) {
   EXPECT_TRUE(ResourcePrefetchPredictor::IsHandledResourceType(
       content::RESOURCE_TYPE_STYLESHEET, "bogus/mime-type"));
   EXPECT_TRUE(ResourcePrefetchPredictor::IsHandledResourceType(
       content::RESOURCE_TYPE_STYLESHEET, ""));
   EXPECT_FALSE(ResourcePrefetchPredictor::IsHandledResourceType(
       content::RESOURCE_TYPE_WORKER, "text/css"));
   EXPECT_FALSE(ResourcePrefetchPredictor::IsHandledResourceType(
@@ skipping 213 matching lines @@
   url_request_job_factory_.set_response_info(response_info);
   std::unique_ptr<net::URLRequest> request_etag =
       CreateURLRequest(GURL("http://www.google.com/cat.png"), net::MEDIUM,
                        content::RESOURCE_TYPE_PREFETCH, 1, 1, true);
   EXPECT_TRUE(URLRequestSummary::SummarizeResponse(*request_etag, &summary));
   EXPECT_TRUE(summary.has_validators);
   EXPECT_TRUE(summary.always_revalidate);
 }
 
 }  // namespace predictors