Re-enable OpenImageFiles/FileManagerBrowserTest

Disabled test, but fixed in issue 829310. Running this test locally in
DEBUG, no flakes. Re-enable this test on all chrome-os bots.

Mash browser tests do not support this test (see patch set #2 trys) so
disable it in mash.

Bug: 836254,711290
Change-Id: Ieac0fea5b568f738fda04bddc8c8dcc488f83887
Reviewed-on: https://chromium-review.googlesource.com/1028534
Commit-Queue: Noel Gordon <noel@chromium.org>
Reviewed-by: Stuart Langley <slangley@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553840}

chrome/browser/chromeos/file_manager/file_manager_browsertest.cc

@@ -123,10 +123,8 @@ WRAPPED_INSTANTIATE_TEST_CASE_P(
         TestParameter(NOT_IN_GUEST_MODE,
                       "audioRepeatOneModeMultipleFileDrive")));
 
-// Fails on official build. http://crbug.com/429294
-// Flaky: http://crbug.com/711290
 WRAPPED_INSTANTIATE_TEST_CASE_P(
-    DISABLED_OpenImageFiles,
+    OpenImageFiles,
     FileManagerBrowserTest,
     ::testing::Values(TestParameter(IN_GUEST_MODE, "imageOpenDownloads"),
                       TestParameter(NOT_IN_GUEST_MODE, "imageOpenDownloads"),

testing/buildbot/filters/mash.browser_tests.filter

@@ -321,6 +321,7 @@
 -DirectoryTreeContextMenu/FileManagerBrowserTest.*
 -RestoreGeometry/FileManagerBrowserTest.*
 -OpenAudioFiles/FileManagerBrowserTest.*
+-OpenImageFiles/FileManagerBrowserTest.*
 -Delete/FileManagerBrowserTest.*
 -SortColumns/FileManagerBrowserTest.*
 -KeyboardOperations/FileManagerBrowserTest.*