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

chrome/browser/extensions/web_view_browsertest.cc

Index: chrome/browser/extensions/web_view_browsertest.cc
diff --git a/chrome/browser/extensions/web_view_browsertest.cc b/chrome/browser/extensions/web_view_browsertest.cc
index 158fc3e937287c9d1af7f7933a23b0fbed04096e..5c9008839725b9338ee09cf53c758d53d6161bfa 100644
--- a/chrome/browser/extensions/web_view_browsertest.cc
+++ b/chrome/browser/extensions/web_view_browsertest.cc
@@ -282,6 +282,8 @@ IN_PROC_BROWSER_TEST_F(WebViewTest, CookieIsolation) {
                               named_partition_contents1,
                               &cookie_size, &cookie_value);
   EXPECT_EQ("", cookie_value);
+
+  CloseShellWindowsAndWaitForAppToExit();
 }
 
 // This tests that in-memory storage partitions are reset on browser restart,
@@ -372,6 +374,8 @@ IN_PROC_BROWSER_TEST_F(WebViewTest, PRE_StoragePersistence) {
                               persistent_partition_contents3,
                               &cookie_size, &cookie_value);
   EXPECT_EQ("persist2=true", cookie_value);
+
+  CloseShellWindowsAndWaitForAppToExit();
 }
 
 // This is the post-reset portion of the StoragePersistence test.  See
@@ -433,6 +437,8 @@ IN_PROC_BROWSER_TEST_F(WebViewTest, StoragePersistence) {
                               persistent_partition_contents3,
                               &cookie_size, &cookie_value);
   EXPECT_EQ("persist2=true", cookie_value);
+
+  CloseShellWindowsAndWaitForAppToExit();
 }
 
 // This tests DOM storage isolation for packaged apps with webview tags. It
@@ -521,6 +527,8 @@ IN_PROC_BROWSER_TEST_F(WebViewTest, DOMStorageIsolation) {
       default_tag_contents1->GetRenderViewHost(), std::wstring(),
       get_session_storage.c_str(), &output));
   EXPECT_STREQ("badval", output.c_str());
+
+  CloseShellWindowsAndWaitForAppToExit();
 }
 
 // This tests IndexedDB isolation for packaged apps with webview tags. It loads
@@ -607,4 +615,6 @@ IN_PROC_BROWSER_TEST_F(WebViewTest, IndexedDBIsolation) {
   ExecuteScriptWaitForTitle(chrome::GetWebContentsAt(browser(), 0),
                             script, "db not found");
   ExecuteScriptWaitForTitle(default_tag_contents1, script, "db not found");
+
+  CloseShellWindowsAndWaitForAppToExit();
 }