Use a scoped temp dir for page load metrics download test

chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc

 // Copyright (c) 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 "base/files/scoped_temp_dir.h"
 #include "base/macros.h"
 #include "base/test/histogram_tester.h"
 #include "base/time/time.h"
 #include "chrome/browser/page_load_metrics/metrics_web_contents_observer.h"
 #include "chrome/browser/page_load_metrics/observers/aborts_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/core_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/document_write_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/no_state_prefetch_page_load_metrics_observer.h"
 #include "chrome/browser/prerender/prerender_histograms.h"
 #include "chrome/browser/prerender/prerender_origin.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_navigator_params.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
+#include "chrome/common/pref_names.h"
 #include "chrome/common/url_constants.h"
 #include "chrome/test/base/in_process_browser_test.h"
 #include "chrome/test/base/ui_test_utils.h"
+#include "components/prefs/pref_service.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/test/browser_test_utils.h"
 #include "content/public/test/download_test_observer.h"
 #include "net/http/failing_http_transaction_factory.h"
 #include "net/http/http_cache.h"
 #include "net/test/embedded_test_server/embedded_test_server.h"
 #include "net/test/url_request/url_request_failed_job.h"
 #include "net/url_request/url_request_context.h"
 #include "net/url_request/url_request_context_getter.h"
 
@@ skipping 134 matching lines @@
 
   ui_test_utils::NavigateToURL(browser(),
                                embedded_test_server()->GetURL("/page204.html"));
   NavigateToUntrackedUrl();
   EXPECT_TRUE(NoPageLoadMetricsRecorded());
 }
 
 IN_PROC_BROWSER_TEST_F(PageLoadMetricsBrowserTest, IgnoreDownloads) {
   ASSERT_TRUE(embedded_test_server()->Start());
 
+  base::ScopedTempDir downloads_directory;
+  ASSERT_TRUE(downloads_directory.CreateUniqueTempDir());
+  browser()->profile()->GetPrefs()->SetFilePath(
+      prefs::kDownloadDefaultDirectory, downloads_directory.GetPath());
   content::DownloadTestObserverTerminal downloads_observer(
       content::BrowserContext::GetDownloadManager(browser()->profile()),
       1,  // == wait_count (only waiting for "download-test3.gif").
       content::DownloadTestObserver::ON_DANGEROUS_DOWNLOAD_FAIL);
 
   ui_test_utils::NavigateToURL(
       browser(), embedded_test_server()->GetURL("/download-test3.gif"));
   downloads_observer.WaitForFinished();
 
   NavigateToUntrackedUrl();
@@ skipping 336 matching lines @@
 
   histogram_tester_.ExpectTotalCount(
       prerender::PrerenderHistograms::GetFirstContentfulPaintHistogramName(
           prerender::ORIGIN_NONE, false, true, base::TimeDelta()),
       1);
   histogram_tester_.ExpectTotalCount(
       prerender::PrerenderHistograms::GetFirstContentfulPaintHistogramName(
           prerender::ORIGIN_NONE, false, false, base::TimeDelta()),
       0);
 }