Fix primary cause of flakiness of DumpAccessibilityEvents tests on Win

content/browser/accessibility/dump_accessibility_browsertest_base.cc

 // Copyright 2014 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 "content/browser/accessibility/dump_accessibility_browsertest_base.h"
 
 #include <set>
 #include <string>
 #include <vector>
 
@@ skipping 177 matching lines @@
 
 void DumpAccessibilityTestBase::RunTestForPlatform(
     const base::FilePath file_path, const char* file_dir) {
   formatter_.reset(CreateAccessibilityTreeFormatter());
 
   // Disable the "hot tracked" state (set when the mouse is hovering over
   // an object) because it makes test output change based on the mouse position.
   BrowserAccessibilityStateImpl::GetInstance()->
       set_disable_hot_tracking_for_testing(true);
 
+  // Normally we avoid firing accessibility focus events when the containing
+  // native window isn't focused. Suppress this check to avoid flaky tests,
+  // since we can't always control when a native window loses focus.
+  BrowserAccessibilityManager::NeverSuppressFocusEventsForTesting();
+
   NavigateToURL(shell(), GURL(url::kAboutBlankURL));
 
   std::string html_contents;
   base::FilePath expected_file;
   std::string expected_contents_raw;
   {
     base::ThreadRestrictions::ScopedAllowIO allow_io_for_test_setup;
     base::ReadFileToString(file_path, &html_contents);
 
     // Read the expected file.
@@ skipping 182 matching lines @@
             static_cast<int>(actual_contents.size()));
       LOG(INFO) << "Wrote expectations to: "
                 << expected_file.LossyDisplayName();
     }
   } else {
     LOG(INFO) << "Test output matches expectations.";
   }
 }
 
 }  // namespace content