Background tracing: Tracing scenarios can now enable/disable Blink features, for A/B testing purpos…

content/browser/tracing/background_tracing_manager_browsertest.cc

Index: content/browser/tracing/background_tracing_manager_browsertest.cc
diff --git a/content/browser/tracing/background_tracing_manager_browsertest.cc b/content/browser/tracing/background_tracing_manager_browsertest.cc
index 1618a7d0dac10816cd6bb38abf3e273e0dbe6291..44d82e78a058e70a65a90dbfa9289eb88b2a5628 100644
--- a/content/browser/tracing/background_tracing_manager_browsertest.cc
+++ b/content/browser/tracing/background_tracing_manager_browsertest.cc
@@ -3,11 +3,13 @@
 // found in the LICENSE file.
 
 #include "base/bind.h"
+#include "base/command_line.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/pattern.h"
 #include "base/trace_event/trace_event.h"
 #include "content/browser/tracing/background_tracing_manager_impl.h"
 #include "content/browser/tracing/background_tracing_rule.h"
+#include "content/public/common/content_switches.h"
 #include "content/public/test/content_browser_test.h"
 #include "content/public/test/content_browser_test_utils.h"
 #include "content/public/test/test_utils.h"
@@ -415,6 +417,94 @@ IN_PROC_BROWSER_TEST_F(BackgroundTracingManagerBrowserTest,
   }
 }
 
+// This tests that toggling Blink scenarios in the config alters the
+// command-line.
+IN_PROC_BROWSER_TEST_F(BackgroundTracingManagerBrowserTest,
+                       ToggleBlinkScenarios) {
+  {
+    SetupBackgroundTracingManager();
+
+    base::RunLoop run_loop;
+    BackgroundTracingManagerUploadConfigWrapper upload_config_wrapper(
+        run_loop.QuitClosure());
+
+    base::DictionaryValue dict;
+    dict.SetString("mode", "PREEMPTIVE_TRACING_MODE");
+    dict.SetString("category", "BENCHMARK");
+
+    scoped_ptr<base::ListValue> rules_list(new base::ListValue());
+    {
+      scoped_ptr<base::DictionaryValue> rules_dict(new base::DictionaryValue());
+      rules_dict->SetString("rule", "MONITOR_AND_DUMP_WHEN_TRIGGER_NAMED");
+      rules_dict->SetString("trigger_name", "test2");
+      rules_list->Append(rules_dict.Pass());
+    }
+
+    dict.Set("configs", rules_list.Pass());
+    dict.SetString("enable_blink_features", "FasterWeb1,FasterWeb2");
+    dict.SetString("disable_blink_features", "SlowerWeb1,SlowerWeb2");
+    scoped_ptr<BackgroundTracingConfig> config(
+        BackgroundTracingConfigImpl::FromDict(&dict));
+    EXPECT_TRUE(config);
+
+    bool scenario_activated =
+        BackgroundTracingManager::GetInstance()->SetActiveScenario(
+            config.Pass(), upload_config_wrapper.get_receive_callback(),
+            BackgroundTracingManager::NO_DATA_FILTERING);
+
+    EXPECT_TRUE(scenario_activated);
+
+    base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
+    EXPECT_TRUE(command_line);
+
+    EXPECT_EQ(command_line->GetSwitchValueASCII(switches::kEnableBlinkFeatures),
+              "FasterWeb1,FasterWeb2");
+    EXPECT_EQ(
+        command_line->GetSwitchValueASCII(switches::kDisableBlinkFeatures),
+        "SlowerWeb1,SlowerWeb2");
+  }
+}
+
+// This tests that toggling Blink scenarios in a scenario won't activate
+// if there's already Blink features toggled by something else (about://flags)
+IN_PROC_BROWSER_TEST_F(BackgroundTracingManagerBrowserTest,
+                       ToggleBlinkScenariosNotOverridingSwitches) {
+  SetupBackgroundTracingManager();
+
+  base::RunLoop run_loop;
+  BackgroundTracingManagerUploadConfigWrapper upload_config_wrapper(
+      run_loop.QuitClosure());
+
+  base::DictionaryValue dict;
+  dict.SetString("mode", "PREEMPTIVE_TRACING_MODE");
+  dict.SetString("category", "BENCHMARK");
+
+  scoped_ptr<base::ListValue> rules_list(new base::ListValue());
+  {
+    scoped_ptr<base::DictionaryValue> rules_dict(new base::DictionaryValue());
+    rules_dict->SetString("rule", "MONITOR_AND_DUMP_WHEN_TRIGGER_NAMED");
+    rules_dict->SetString("trigger_name", "test2");
+    rules_list->Append(rules_dict.Pass());
+  }
+
+  dict.Set("configs", rules_list.Pass());
+  dict.SetString("enable_blink_features", "FasterWeb1,FasterWeb2");
+  dict.SetString("disable_blink_features", "SlowerWeb1,SlowerWeb2");
+  scoped_ptr<BackgroundTracingConfig> config(
+      BackgroundTracingConfigImpl::FromDict(&dict));
+  EXPECT_TRUE(config);
+
+  base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+      switches::kEnableBlinkFeatures, "FooFeature");
+
+  bool scenario_activated =
+      BackgroundTracingManager::GetInstance()->SetActiveScenario(
+          config.Pass(), upload_config_wrapper.get_receive_callback(),
+          BackgroundTracingManager::NO_DATA_FILTERING);
+
+  EXPECT_FALSE(scenario_activated);
+}
+
 // This tests that delayed histogram triggers triggers work as expected
 // with preemptive scenarios.
 IN_PROC_BROWSER_TEST_F(BackgroundTracingManagerBrowserTest,