Reland of Disable flaky CommandLineExtensionsDontLoad test (patchset #1 id:1...

Reland of Disable flaky CommandLineExtensionsDontLoad test (patchset #1 id:1 of https://codereview.chromium.org/2855553002/ )

Reason for revert:
Build failure causing original revert seems to have been a flake.

Original issue's description:
> Revert of Disable flaky CommandLineExtensionsDontLoad test (patchset #1 id:1 of https://codereview.chromium.org/2852933002/ )
>
> Reason for revert:
> Speculatively reverting due to build failure on Mac https://build.chromium.org/p/chromium/builders/Mac/builds/26841
>
> Original issue's description:
> > Disable flaky CommandLineExtensionsDontLoad test
> >
> > TBR=emaxx@chromium.org
> > BUG=716727
> >
> > Review-Url: https://codereview.chromium.org/2852933002
> > Cr-Commit-Position: refs/heads/master@{#468286}
> > Committed: https://chromium.googlesource.com/chromium/src/+/91f64acccbfe592af367f79ae74649d520528f0b
>
> TBR=emaxx@chromium.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=716727
>
> Review-Url: https://codereview.chromium.org/2855553002
> Cr-Commit-Position: refs/heads/master@{#468290}
> Committed: https://chromium.googlesource.com/chromium/src/+/606b2b5d25564f187a843d25e5c2998d4ad2c04e

TBR=emaxx@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=716727

Review-Url: https://codereview.chromium.org/2848223002
Cr-Commit-Position: refs/heads/master@{#468300}

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(