Avoid file IO on UI thread by moving more save-page-as stuff to the FILE thread.

chrome/browser/download/save_page_browsertest.cc

Index: chrome/browser/download/save_page_browsertest.cc
diff --git a/chrome/browser/download/save_page_browsertest.cc b/chrome/browser/download/save_page_browsertest.cc
index 544d49935ad23def57a279a2ebfcfeb6611b5b31..c196bae2aba20a7325ec6cb96d425700bbe84dbb 100644
--- a/chrome/browser/download/save_page_browsertest.cc
+++ b/chrome/browser/download/save_page_browsertest.cc
@@ -20,6 +20,7 @@
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/test/test_file_util.h"
+#include "base/threading/thread_restrictions.h"
 #include "build/build_config.h"
 #include "chrome/app/chrome_command_ids.h"
 #include "chrome/browser/download/chrome_download_manager_delegate.h"
@@ -726,8 +727,10 @@ IN_PROC_BROWSER_TEST_F(SavePageAsMHTMLBrowserTest, SavePageAsMHTML) {
   SavePackageFinishedObserver observer(
       content::BrowserContext::GetDownloadManager(browser()->profile()),
       loop_runner->QuitClosure());
+  bool old_io_allowed_value = base::ThreadRestrictions::SetIOAllowed(false);
   chrome::SavePage(browser());
   loop_runner->Run();
+  base::ThreadRestrictions::SetIOAllowed(old_io_allowed_value);

[Łukasz Anforowicz, 2016/07/26 22:30:50]

I've reverted these changes in a more recent patchset - I am instead doing the
IO asserts on a broader scale in https://codereview.chromium.org/2175933002/
(this is for content_browsertests;  if this goes well, then maybe I'll also try
chrome layer's browser_tests in https://codereview.chromium.org/2175933002).

   ASSERT_TRUE(VerifySavePackageExpectations(browser(), url));
   persisted.WaitForPersisted();
 
@@ -751,8 +754,10 @@ IN_PROC_BROWSER_TEST_F(SavePageBrowserTest, SavePageBrowserTest_NonMHTML) {
   SavePackageFinishedObserver observer(
       content::BrowserContext::GetDownloadManager(browser()->profile()),
       loop_runner->QuitClosure());
+  bool old_io_allowed_value = base::ThreadRestrictions::SetIOAllowed(false);
   chrome::SavePage(browser());
   loop_runner->Run();
+  base::ThreadRestrictions::SetIOAllowed(old_io_allowed_value);
   base::FilePath download_dir = DownloadPrefs::FromDownloadManager(
       GetDownloadManager())->DownloadPath();
   base::FilePath filename = download_dir.AppendASCII("dataurl.txt");