Fix some more tests that were writing to the user's home directory.

chrome/browser/policy/policy_browsertest.cc

 // Copyright (c) 2012 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 <algorithm>
 #include <string>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 1674 matching lines @@
 #endif
 IN_PROC_BROWSER_TEST_F(PolicyTest, MAYBE_ExtensionInstallSources) {
   CommandLine::ForCurrentProcess()->AppendSwitchASCII(
       switches::kAppsGalleryInstallAutoConfirmForTests, "accept");
 
   const GURL install_source_url(URLRequestMockHTTPJob::GetMockUrl(
       base::FilePath(FILE_PATH_LITERAL("extensions/*"))));
   const GURL referrer_url(URLRequestMockHTTPJob::GetMockUrl(
       base::FilePath(FILE_PATH_LITERAL("policy/*"))));
 
+  base::ScopedTempDir download_directory;
+  ASSERT_TRUE(download_directory.CreateUniqueTempDir());
+  DownloadPrefs* download_prefs =
+      DownloadPrefs::FromBrowserContext(browser()->profile());
+  download_prefs->SetDownloadPath(download_directory.path());
+
   const GURL download_page_url(URLRequestMockHTTPJob::GetMockUrl(base::FilePath(
       FILE_PATH_LITERAL("policy/extension_install_sources_test.html"))));
   ui_test_utils::NavigateToURL(browser(), download_page_url);
 
   // As long as the policy is not present, extensions are considered dangerous.
   content::DownloadTestObserverTerminal download_observer(
       content::BrowserContext::GetDownloadManager(browser()->profile()), 1,
       content::DownloadTestObserver::ON_DANGEROUS_DOWNLOAD_DENY);
   PerformClick(0, 0);
   download_observer.WaitForFinished();
@@ skipping 1256 matching lines @@
   PrefService* prefs = browser()->profile()->GetPrefs();
   EXPECT_TRUE(extensions::NativeMessageProcessHost::IsHostAllowed(
       prefs, "host.name"));
   EXPECT_FALSE(extensions::NativeMessageProcessHost::IsHostAllowed(
       prefs, "other.host.name"));
 }
 
 #endif  // !defined(CHROME_OS)
 
 }  // namespace policy