Disable SecurityStyleChangedTest.SecurityStyleChangedObserverGoBack on ChromeOS due to flakiness.

chrome/browser/ssl/chrome_security_state_model_client_browser_tests.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ssl/chrome_security_state_model_client.h"
 
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/strings/string_split.h"
@@ skipping 974 matching lines @@
                           INVALID_CERTIFICATE, browser());
   EXPECT_TRUE(observer.latest_explanations().scheme_is_cryptographic);
   EXPECT_FALSE(observer.latest_explanations().pkp_bypassed);
   EXPECT_TRUE(observer.latest_explanations().info_explanations.empty());
   EXPECT_FALSE(observer.latest_explanations().displayed_insecure_content);
   EXPECT_FALSE(observer.latest_explanations().ran_insecure_content);
 }
 
 // Visit a valid HTTPS page, then a broken HTTPS page, and then go back,
 // and test that the observed security style matches.
+#if defined(OS_CHROMEOS)
+// Flaky on Chrome OS. See https://crbug.com/638576.
+#define MAYBE_SecurityStyleChangedObserverGoBack \
+  DISABLED_SecurityStyleChangedObserverGoBack
+#else
+#define MAYBE_SecurityStyleChangedObserverGoBack \
+  SecurityStyleChangedObserverGoBack
+#endif
 IN_PROC_BROWSER_TEST_F(SecurityStyleChangedTest,
-                       SecurityStyleChangedObserverGoBack) {
+                       MAYBE_SecurityStyleChangedObserverGoBack) {
   ASSERT_TRUE(https_server_.Start());
 
   net::EmbeddedTestServer https_test_server_expired(
       net::EmbeddedTestServer::TYPE_HTTPS);
   https_test_server_expired.SetSSLConfig(net::EmbeddedTestServer::CERT_EXPIRED);
   https_test_server_expired.ServeFilesFromSourceDirectory(
       base::FilePath(kDocRoot));
   ASSERT_TRUE(https_test_server_expired.Start());
 
   content::WebContents* web_contents =
@@ skipping 331 matching lines @@
   ChromeSecurityStateModelClient* model_client =
       ChromeSecurityStateModelClient::FromWebContents(web_contents);
   ASSERT_TRUE(model_client);
   const SecurityStateModel::SecurityInfo& security_info =
       model_client->GetSecurityInfo();
   EXPECT_EQ(SecurityStateModel::SECURE, security_info.security_level);
   EXPECT_EQ(kTestSCTStatuses, security_info.sct_verify_statuses);
 }
 
 }  // namespace