Fix integration tests in src/chrome and src/extensions so that we can turn on IO thread checks wi...

chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc

Index: chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc
diff --git a/chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc b/chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc
index 8d69c71e8ddf51c0cebb4c566fda09100271e219..f7fc55f7a54d2dd7833e4e8ff40d62b2472e942f 100644
--- a/chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc
+++ b/chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc
@@ -5,6 +5,7 @@
 #include "base/files/scoped_temp_dir.h"
 #include "base/macros.h"
 #include "base/test/histogram_tester.h"
+#include "base/threading/thread_restrictions.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"
@@ -319,6 +320,7 @@ IN_PROC_BROWSER_TEST_F(PageLoadMetricsBrowserTest, Ignore204Pages) {
 IN_PROC_BROWSER_TEST_F(PageLoadMetricsBrowserTest, IgnoreDownloads) {
   ASSERT_TRUE(embedded_test_server()->Start());
 
+  base::ThreadRestrictions::ScopedAllowIO allow_io;
   base::ScopedTempDir downloads_directory;
   ASSERT_TRUE(downloads_directory.CreateUniqueTempDir());
   browser()->profile()->GetPrefs()->SetFilePath(