Re-enable flaky viz_browser_tests

A while back there were a series of viz_browser_tests that were timing out on
Windows trybots.

There was no stack traces at the time. We could no reproduce these locally.
However there were a bunch of other timeouts happening on Windows outside of
viz configurations at the time.

This speculatively re-enables those tests.

viz_browser_tests is not currently on Windows CQ so Windows related failures
will only affect our FYI bots.

TBR=kylechar@chromium.org
TEST=viz_browser_tests

Bug: 821029
Change-Id: I8a1d3369915da11e0110c9bf9611d0130fb8f470
Reviewed-on: https://chromium-review.googlesource.com/1060417Reviewed-by: Jonathan Ross <jonross@chromium.org>
Commit-Queue: Jonathan Ross <jonross@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558867}

testing/buildbot/filters/viz.browser_tests.filter

@@ -36,18 +36,6 @@
 # Incorrect Focus State crbug.com/818205
 -WebViewFocusBrowserPluginSpecificTest.TouchFocusesEmbedder
 
-# Windows timeouts. https://crbug.com/821029
--BrowserNavigatorTest.Disposition_NewPopupFromAppPopup
--ExtensionApiCaptureTest.CaptureNullWindow
--ManifestVerifierBrowserTest.*
--OmniboxPopupContentsViewTest.ThemeIntegration/*
--PDFIsolatedExtensionTest.MultipleDomains
--PrefHashBrowserTest*
--StartupBrowserCreatorTest.ProfilesWithoutPagesNotLaunched
--UserInitiatedRunsDisabled*
--UserInitiatedRunsEnabled*
--WithVaryingSeeds/ChromeCleanerPromptUserTest.*
-
 # Mac
 # Shutdown error. https://crbug.com/823276
 -PluginPowerSaverBrowserTest.SmallerThanPlayIcon