Reenable test CommandLineExtensionsDontLoad everywhere except on Mash

The ExtensionsLoadTestWithLoginScreenApps.CommandLineExtensionsDontLoad
test was failing in mash_browsertests. According to some investigation,
it may be due to the problem not with the test itself, but with the test
suite (see https://crbug.com/716727#c6).

Therefore enabling the test, but with blacklisting it from running in
mash_browsertests.

Bug: 716727
Change-Id: I0860b9efbcfd5a333464a2567273a962d0957a5e
Reviewed-on: https://chromium-review.googlesource.com/503351Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Jonathan Ross <jonross@chromium.org>
Commit-Queue: Maksim Ivanov <emaxx@chromium.org>
Cr-Commit-Position: refs/heads/master@{#473385}

chrome/browser/extensions/extension_startup_browsertest.cc

@@ -273,9 +273,8 @@ IN_PROC_BROWSER_TEST_F(ExtensionsLoadTest, Test) {
 
 #if defined(OS_CHROMEOS)
 
-// Flaky test crbug.com/716727
 IN_PROC_BROWSER_TEST_F(ExtensionsLoadTest,
-                       DISABLED_SigninProfileCommandLineExtensionsDontLoad) {
+                       SigninProfileCommandLineExtensionsDontLoad) {
   // The --load-extension command line flag should not be applied to the sign-in
   // profile.
   EXPECT_EQ(0, GetNonComponentEnabledExtensionCount(

testing/buildbot/filters/mash.browser_tests.filter

@@ -11,6 +11,9 @@ BrowserTest.*
 -BrowserTest.JavascriptAlertActivatesTab
 -BrowserTest.Title
 
+# Flaky tests -crbug.com/716727
+-ExtensionsLoadTestWithLoginScreenApps.CommandLineExtensionsDontLoad
+
 # Trying to whitelist
 AppWindowApiTest.AlphaEnabledHasPermissions
 AppWindowApiTest.AlphaEnabledInStable
@@ -122,7 +125,6 @@ ExecuteDefaultTaskOnDownloads/FileManagerBrowserTest.Test/0
 ExecuteDefaultTaskOnDownloads/FileManagerBrowserTest.Test/1
 ExecuteDefaultTaskOnDrive/FileManagerBrowserTest.Test/0
 ExtensionDetermineDownloadFilenameInternal.ExtensionDetermineDownloadFilenameInternal
-ExtensionsLoadTestWithLoginScreenApps.CommandLineExtensionsDontLoad
 FolderShortcuts/FileManagerBrowserTest.Test/0
 FolderShortcuts/FileManagerBrowserTest.Test/1
 FormAutocompleteTest.AjaxSucceeded_FilledFormIsInvisible