Disable flaky CommandLineExtensionsDontLoad test

TBR=emaxx@chromium.org
BUG=716727

Review-Url: https://codereview.chromium.org/2852933002
Cr-Commit-Position: refs/heads/master@{#468286}

chrome/browser/extensions/extension_startup_browsertest.cc

@@ -284,8 +284,9 @@ class ExtensionsLoadTestWithLoginScreenApps : public ExtensionsLoadTest {
   }
 };
 
+// Flaky test crbug.com/716727
 IN_PROC_BROWSER_TEST_F(ExtensionsLoadTestWithLoginScreenApps,
-                       CommandLineExtensionsDontLoad) {
+                       DISABLED_CommandLineExtensionsDontLoad) {
   // The --load-extension command line flag should not be applied to the sign-in
   // profile.
   EXPECT_EQ(0, GetNonComponentEnabledExtensionCount(