Return empty startup tabs for incognito profile.

StartupTabProvider may be called when Chrome starts in an incognito profile,
which leads to a crash at start-up. This CL addresses this and adds a unit
test to make sure it does not regress in the future.

Bug: 769241
Change-Id: Idea489bc05e31d7ac693cb935b1481979099bd09
Reviewed-on: https://chromium-review.googlesource.com/689535Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Mihai Sardarescu <msarda@chromium.org>
Cr-Commit-Position: refs/heads/master@{#505395}

chrome/browser/ui/startup/startup_tab_provider.cc

@@ -71,8 +71,10 @@ StartupTabs StartupTabProviderImpl::GetOnboardingTabs(Profile* profile) const {
       prefs && prefs->GetBoolean(prefs::kHasSeenWelcomePage);
   standard_params.is_signin_allowed = profile->IsSyncAllowed();
   SigninManager* signin_manager = SigninManagerFactory::GetForProfile(profile);
-  standard_params.is_signed_in = signin_manager->IsAuthenticated();
-  standard_params.is_signin_in_progress = signin_manager->AuthInProgress();
+  standard_params.is_signed_in =
+      signin_manager && signin_manager->IsAuthenticated();
+  standard_params.is_signin_in_progress =
+      signin_manager && signin_manager->AuthInProgress();
   standard_params.is_supervised_user = profile->IsSupervised();
 
 #if defined(OS_WIN)

chrome/browser/ui/startup/startup_tab_provider_unittest.cc

@@ -6,6 +6,8 @@
 
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/common/url_constants.h"
+#include "chrome/test/base/testing_profile.h"
+#include "content/public/test/test_browser_thread_bundle.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "url/gurl.h"
 
@@ -443,3 +445,10 @@ TEST(StartupTabProviderTest, GetNewTabPageTabsForState_Negative) {
 
   ASSERT_TRUE(output.empty());
 }
+
+TEST(StartupTabProviderTest, IncognitoProfile) {
+  content::TestBrowserThreadBundle thread_bundle;
+  TestingProfile profile;
+  Profile* incognito = profile.GetOffTheRecordProfile();
+  EXPECT_TRUE(StartupTabProviderImpl().GetOnboardingTabs(incognito).empty());
+}