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

chrome/browser/ui/webui/test_files_request_filter.cc

Index: chrome/browser/ui/webui/test_files_request_filter.cc
diff --git a/chrome/browser/ui/webui/test_files_request_filter.cc b/chrome/browser/ui/webui/test_files_request_filter.cc
index 4c69de566cfd8e41df2ef246ab6fec23e48e0f42..2d5291221d490a4e5a8c874fba68af28f77e4d5c 100644
--- a/chrome/browser/ui/webui/test_files_request_filter.cc
+++ b/chrome/browser/ui/webui/test_files_request_filter.cc
@@ -9,6 +9,7 @@
 #include "base/memory/ref_counted_memory.h"
 #include "base/path_service.h"
 #include "base/strings/string_split.h"
+#include "base/threading/thread_restrictions.h"
 #include "chrome/common/chrome_paths.h"
 
 namespace {
@@ -16,6 +17,7 @@ namespace {
 bool HandleTestFileRequestCallback(
     const std::string& path,
     const content::WebUIDataSource::GotDataCallback& callback) {
+  base::ThreadRestrictions::ScopedAllowIO allow_io;
   std::vector<std::string> url_substr =
       base::SplitString(path, "/", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
   if (url_substr.size() != 2 || url_substr[0] != "test")