CrExtensionsPackDialogTest.PackSuccess is flaky on Windows

Conditionally disables this test on OS_WIN.

BUG=832885
TBR=rdevlin.cronin@chromium.org
NO-TRY=True

Change-Id: Ic2a069cfdc4a07d42cf06af42919c7a20947c278
Reviewed-on: https://chromium-review.googlesource.com/1012994Reviewed-by: Matthew Wolenetz <wolenetz@chromium.org>
Commit-Queue: Matthew Wolenetz <wolenetz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550760}

chrome/test/data/webui/extensions/cr_extensions_browsertest.js

@@ -520,7 +520,14 @@ TEST_F('CrExtensionsPackDialogTest', 'Interaction', function() {
   this.runMochaTest(extension_pack_dialog_tests.TestNames.Interaction);
 });
 
-TEST_F('CrExtensionsPackDialogTest', 'PackSuccess', function() {
+// Disabling on Windows due to flaky timeout on some build bots.
+// http://crbug.com/832885
+GEN('#if defined(OS_WIN)');
+GEN('#define MAYBE_PackSuccess DISABLED_PackSuccess');
+GEN('#else');
+GEN('#define MAYBE_PackSuccess PackSuccess');
+GEN('#endif');
+TEST_F('CrExtensionsPackDialogTest', 'MAYBE_PackSuccess', function() {
   this.runMochaTest(extension_pack_dialog_tests.TestNames.PackSuccess);
 });