Remove dependency from SignInBrowsertest on tracing events watching

chrome/browser/chromeos/login/login_browsertest.cc

Index: chrome/browser/chromeos/login/login_browsertest.cc
diff --git a/chrome/browser/chromeos/login/login_browsertest.cc b/chrome/browser/chromeos/login/login_browsertest.cc
index eb75a67b0ce33767c118b569316b61b2e7dd9f37..aca04ed5c4ab8491a0a0b1916d30f1965fb54e78 100644
--- a/chrome/browser/chromeos/login/login_browsertest.cc
+++ b/chrome/browser/chromeos/login/login_browsertest.cc
@@ -6,6 +6,7 @@
 #include "ash/shell.h"
 #include "base/command_line.h"
 #include "base/location.h"
+#include "base/run_loop.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/string_util.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ -19,11 +20,11 @@
 #include "chrome/browser/profiles/profile_manager.h"
 #include "chrome/browser/profiles/profiles_state.h"
 #include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/webui/chromeos/login/signin_screen_handler.h"
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/test/base/in_process_browser_test.h"
 #include "chrome/test/base/interactive_test_utils.h"
-#include "chrome/test/base/tracing.h"
 #include "chromeos/chromeos_switches.h"
 #include "chromeos/login/user_names.h"
 #include "chromeos/settings/cros_settings_names.h"
@@ -86,10 +87,17 @@ class LoginSigninTest : public InProcessBrowserTest {
 
   void SetUpOnMainThread() override {
     LoginDisplayHostImpl::DisableRestrictiveProxyCheckForTest();
+    run_loop_.reset(new base::RunLoop());
+    SigninScreenHandler::SetCallbackOnUiShownForTesting(
+        base::Bind(&LoginSigninTest::OnLoginUiShown, base::Unretained(this)));
+  }
 
-    ASSERT_TRUE(tracing::BeginTracingWithWatch(
-        "ui", "ui", "ShowLoginWebUI", 1));
+  void OnLoginUiShown() {
+    DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+    run_loop_->QuitClosure().Run();
   }
+
+  std::unique_ptr<base::RunLoop> run_loop_;
 };
 
 class LoginTest : public LoginManagerTest {
@@ -245,10 +253,7 @@ IN_PROC_BROWSER_TEST_F(LoginCursorTest, CursorHidden) {
 
 // Verifies that the webui for login comes up successfully.
 IN_PROC_BROWSER_TEST_F(LoginSigninTest, WebUIVisible) {
-  base::TimeDelta no_timeout;
-  EXPECT_TRUE(tracing::WaitForWatchEvent(no_timeout));
-  std::string json_events;
-  ASSERT_TRUE(tracing::EndTracing(&json_events));
+  run_loop_->Run();
 }