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

chrome/browser/extensions/extension_apitest.cc

Index: chrome/browser/extensions/extension_apitest.cc
diff --git a/chrome/browser/extensions/extension_apitest.cc b/chrome/browser/extensions/extension_apitest.cc
index f70b3b12768c29246d9d2cbd02a4ed3c31b930c9..4d1b926aa4ce3a7d4a0983b9e4d383f30d077611 100644
--- a/chrome/browser/extensions/extension_apitest.cc
+++ b/chrome/browser/extensions/extension_apitest.cc
@@ -6,8 +6,9 @@
 
 #include "base/string_util.h"
 #include "base/stringprintf.h"
-#include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/api/test/test_api.h"
+#include "chrome/browser/extensions/extension_service.h"
+#include "chrome/browser/extensions/platform_app_service.h"
 #include "chrome/browser/extensions/unpacked_installer.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser.h"
@@ -173,6 +174,14 @@ bool ExtensionApiTest::RunPageTest(const std::string& page_url,
 }
 
 bool ExtensionApiTest::RunPlatformAppTest(const char* extension_name) {
+  bool res = RunPlatformAppTestReturnImmediately(extension_name);
+  CloseShellWindowsAndWaitForAppToExit();
+  return res;
+}
+
+bool ExtensionApiTest::RunPlatformAppTestReturnImmediately(
+    const char* extension_name) {
+  extensions::PlatformAppService::CreateInstance(browser()->profile());
   return RunExtensionTestImpl(extension_name, "", kFlagLaunchPlatformApp);
 }