Ensure tests have an active task runner

chrome/browser/lifetime/application_lifetime.cc

Index: chrome/browser/lifetime/application_lifetime.cc
diff --git a/chrome/browser/lifetime/application_lifetime.cc b/chrome/browser/lifetime/application_lifetime.cc
index ac9ff01f43aa4ea60b611be98da1c58cd94896a6..0e87a2cf5f989f15ce87af7c4c2f9685d6c8b251 100644
--- a/chrome/browser/lifetime/application_lifetime.cc
+++ b/chrome/browser/lifetime/application_lifetime.cc
@@ -82,6 +82,7 @@ bool AreAllBrowsersCloseable() {
 #endif  // !defined(OS_ANDROID)
 
 int g_keep_alive_count = 0;
+bool g_disable_shutdown_for_testing = false;
 
 #if defined(OS_CHROMEOS)
 // Whether chrome should send stop request to a session manager.
@@ -332,11 +333,11 @@ void DecrementKeepAliveCount() {
   if (!WillKeepAlive()) {
     g_browser_process->ReleaseModule();
     // If there are no browsers open and we aren't already shutting down,
-    // initiate a shutdown. Also skips shutdown if this is a unit test
-    // (MessageLoop::current() == null).
+    // initiate a shutdown. Also skips shutdown if this is a unit test.
+    // (MessageLoop::current() == null or explicitly disabled).
     if (chrome::GetTotalBrowserCount() == 0 &&
-        !browser_shutdown::IsTryingToQuit() &&
-        base::MessageLoop::current()) {
+        !browser_shutdown::IsTryingToQuit() && base::MessageLoop::current() &&
+        !g_disable_shutdown_for_testing) {
       CloseAllBrowsers();
     }
   }
@@ -422,4 +423,8 @@ bool ShouldStartShutdown(Browser* browser) {
   return true;
 }
 
+void DisableShutdownForTesting(bool disable_shutdown_for_testing) {
+  g_disable_shutdown_for_testing = disable_shutdown_for_testing;

[Andrew T Wilson (Slow), 2015/04/27 09:48:26]

Should setting this to false also initiate a shutdown using the same criteria as
DecrementKeepAliveCount()?

[Sami, 2015/04/27 11:31:40]

That's a good thought, but unfortunately in BackgroundModeManagerTest it leads
back to the original problem since at the time of this call we don't have the
necessary context to do a proper shutdown (e.g., no MessageCenter instance).

I've now changed this to perform the shutdown like you suggested, but also made
BackgroundModeManagerTest ensure that we don't try to close the browser when we
shouldn't.

+}
+
 }  // namespace chrome