Change default CSD model version

Since we're about to launch version 4 to Stable, set it as the default.
This CL also updates a few tests that implicitly use the default model
version.

Fixed: 1054056
Change-Id: Icb2d781279ac132019ab9bd6d433dbb627490713
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2316335
Commit-Queue: Daniel Rubery <drubery@chromium.org>
Reviewed-by: Bettina Dea <bdea@chromium.org>
Auto-Submit: Daniel Rubery <drubery@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791403}

chrome/browser/safe_browsing/client_side_detection_service_unittest.cc

@@ -397,20 +397,20 @@ TEST_F(ClientSideDetectionServiceTest, TestModelFollowsPrefs) {
   profile_->GetPrefs()->SetBoolean(prefs::kSafeBrowsingEnabled, true);
   ASSERT_NE(csd_service_->model_loader_, nullptr);
   EXPECT_EQ(csd_service_->model_loader_->name(),
-            "client_model_v5_variation_0.pb");
+            "client_model_v5_variation_4.pb");
 
   // Safe Browsing extended reporting is enabled
   profile_->GetPrefs()->SetBoolean(prefs::kSafeBrowsingScoutReportingEnabled,
                                    true);
   ASSERT_NE(csd_service_->model_loader_, nullptr);
   EXPECT_EQ(csd_service_->model_loader_->name(),
-            "client_model_v5_ext_variation_0.pb");
+            "client_model_v5_ext_variation_4.pb");
 
   // Safe Browsing enhanced protection is enabled.
   profile_->GetPrefs()->SetBoolean(prefs::kSafeBrowsingEnhanced, true);
   ASSERT_NE(csd_service_->model_loader_, nullptr);
   EXPECT_EQ(csd_service_->model_loader_->name(),
-            "client_model_v5_ext_variation_0.pb");
+            "client_model_v5_ext_variation_4.pb");
 }
 
 }  // namespace safe_browsing

chrome/browser/safe_browsing/client_side_model_loader.cc

@@ -78,7 +78,7 @@ int ModelLoader::GetModelNumber() {
       kClientModelFinchExperiment, kClientModelFinchParam);
   int model_number = 0;
   if (!base::StringToInt(num_str, &model_number)) {
-    model_number = 0;  // Default model
+    model_number = 4;  // Default model
   }
   return model_number;
 }

chrome/browser/safe_browsing/client_side_model_loader_unittest.cc

@@ -362,14 +362,14 @@ TEST_F(ModelLoaderTest, ModelNamesTest) {
   EXPECT_EQ(ModelLoader::FillInModelName(false, 5),
             "client_model_v5_variation_5.pb");
 
-  // No Finch setup. Should default to 0.
+  // No Finch setup. Should default to 4.
   std::unique_ptr<ModelLoader> loader;
   loader.reset(new ModelLoader(base::Closure(), nullptr,
                                false /* is_extended_reporting */));
-  EXPECT_EQ(loader->name(), "client_model_v5_variation_0.pb");
+  EXPECT_EQ(loader->name(), "client_model_v5_variation_4.pb");
   EXPECT_EQ(loader->url_.spec(),
             "https://ssl.gstatic.com/safebrowsing/csd/"
-            "client_model_v5_variation_0.pb");
+            "client_model_v5_variation_4.pb");
 
   // Model 1, no extended reporting.
   SetFinchModelNumber(1);