Disable InstantExtendedTest.SearchDoesntReuseInstantTab on Windows.

InstantExtendedTest.SearchDoesntReuseInstantTab (run #2):
[ RUN      ] InstantExtendedTest.SearchDoesntReuseInstantTab
[4616:1072:0106/014942.591:ERROR:variations_util.cc(88)] Missing Worker
Pool Configuration: Background
[1156:5048:0106/014942.680:INFO:media_foundation_video_encode_accelerator_win.cc(329)]
Windows versions earlier than 8 are not supported.
[4616:4776:0106/014943.002:WARNING:embedded_test_server.cc(219)] Request
not handled. Returning 404: /favicon.ico
[4616:1072:0106/014943.047:INFO:CONSOLE(1)] "Uncaught ReferenceError:
onMostVisitedChangedCalls is not defined", source:  (1)

BUG=678975
TBR=treib@chromium.org

Review-Url: https://codereview.chromium.org/2613273002
Cr-Commit-Position: refs/heads/master@{#441977}

chrome/browser/ui/search/instant_extended_interactive_uitest.cc

@@ -307,7 +307,13 @@ class InstantPolicyTest : public ExtensionBrowserTest, public InstantTestBase {
   DISALLOW_COPY_AND_ASSIGN(InstantPolicyTest);
 };
 
-IN_PROC_BROWSER_TEST_F(InstantExtendedTest, SearchDoesntReuseInstantTab) {
+// Flaky on Windows in the CQ: https://crbug.com/678975
+#if defined(OS_WIN)
+#define MAYBE_SearchDoesntReuseInstantTab DISABLED_SearchDoesntReuseInstantTab
+#else
+#define MAYBE_SearchDoesntReuseInstantTab SearchDoesntReuseInstantTab
+#endif
+IN_PROC_BROWSER_TEST_F(InstantExtendedTest, MAYBE_SearchDoesntReuseInstantTab) {
   ASSERT_NO_FATAL_FAILURE(SetupInstant(browser()));
   FocusOmnibox();