Keep browser process alive while there are platform apps with background pages running.

chrome/browser/sync/test/integration/single_client_apps_sync_test.cc

Index: chrome/browser/sync/test/integration/single_client_apps_sync_test.cc
diff --git a/chrome/browser/sync/test/integration/single_client_apps_sync_test.cc b/chrome/browser/sync/test/integration/single_client_apps_sync_test.cc
index 320b4a2a79d1f3f8bb2cc023ff9d274f4288c687..ce85aa2079c7de0e2d56d432665fcdae9b85751f 100644
--- a/chrome/browser/sync/test/integration/single_client_apps_sync_test.cc
+++ b/chrome/browser/sync/test/integration/single_client_apps_sync_test.cc
@@ -10,6 +10,7 @@
 using apps_helper::AllProfilesHaveSameAppsAsVerifier;
 using apps_helper::InstallApp;
 using apps_helper::InstallPlatformApp;
+using apps_helper::WaitForPlatformAppsToUnload;
 
 class SingleClientAppsSyncTest : public SyncTest {
  public:
@@ -53,6 +54,8 @@ IN_PROC_BROWSER_TEST_F(SingleClientAppsSyncTest, StartWithSomePlatformApps) {
   ASSERT_TRUE(SetupSync());
 
   ASSERT_TRUE(AllProfilesHaveSameAppsAsVerifier());
+
+  WaitForPlatformAppsToUnload();
 }
 
 IN_PROC_BROWSER_TEST_F(SingleClientAppsSyncTest, InstallSomeLegacyApps) {
@@ -83,6 +86,8 @@ IN_PROC_BROWSER_TEST_F(SingleClientAppsSyncTest, InstallSomePlatformApps) {
       "Waiting for app changes."));
 
   ASSERT_TRUE(AllProfilesHaveSameAppsAsVerifier());
+
+  WaitForPlatformAppsToUnload();
 }
 
 IN_PROC_BROWSER_TEST_F(SingleClientAppsSyncTest, InstallSomeApps) {
@@ -106,4 +111,6 @@ IN_PROC_BROWSER_TEST_F(SingleClientAppsSyncTest, InstallSomeApps) {
       "Waiting for app changes."));
 
   ASSERT_TRUE(AllProfilesHaveSameAppsAsVerifier());
+
+  WaitForPlatformAppsToUnload();
 }