Make URLRequestContextBuilder use base/task_scheduler/

net/url_request/url_request_context_builder.h

Index: net/url_request/url_request_context_builder.h
diff --git a/net/url_request/url_request_context_builder.h b/net/url_request/url_request_context_builder.h
index 2a520017cae85457ef517e3a0daf942eba8e52dc..526ff1f9f0314efdfa5d902d54d41bed722122fe 100644
--- a/net/url_request/url_request_context_builder.h
+++ b/net/url_request/url_request_context_builder.h
@@ -26,6 +26,7 @@
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "base/task_scheduler/task_traits.h"
 #include "build/build_config.h"
 #include "net/base/net_export.h"
 #include "net/base/network_delegate.h"
@@ -42,6 +43,8 @@
 
 namespace base {
 class SingleThreadTaskRunner;
+class SequencedTaskRunner;
+class TaskRunner;
 }
 
 namespace net {
@@ -325,8 +328,8 @@ class NET_EXPORT URLRequestContextBuilder {
       std::unique_ptr<CookieStore> cookie_store,
       std::unique_ptr<ChannelIDService> channel_id_service);
 
-  // Sets the task runner used to perform file operations. If not set, one will
-  // be created.
+  // Sets the task runner used to perform file operations. If not set,
+  // TaskSchedulers will be used instead.
   void SetFileTaskRunner(
       const scoped_refptr<base::SingleThreadTaskRunner>& task_runner);
 
@@ -358,6 +361,15 @@ class NET_EXPORT URLRequestContextBuilder {
       NetworkDelegate* network_delegate,
       NetLog* net_log);
 
+  // Returns a TaskRunner with the specified traits. If |file_task_runner_| is
+  // non-NULL, uses that. Otherwise, uses base/task_scheduler/ and the specified
+  // traits.

[Randy Smith (Not in Mondays), 2017/06/21 12:56:26]

I also find myself wondering if names that captured more of the goals of these
routines for URLRequestContextBuilder (i.e. slightly higher level) might be
better.  I'll mention that now in case it sparks ideas in your mind, but feel
free to ignore the comment--if I still feel that way after I understand the
purposes better I'll make concrete suggestions.

[Randy Smith (Not in Mondays), 2017/06/21 12:56:26]

nit, suggestion: It bothers me a little that we're being specific about using a
file related thingy above (in the setter) but the naming of these methods
doesn't mention that it's for file operations.  WDYT about including "File" in
the names?

[mmenke, 2017/06/21 15:13:56]

I'm open to other ideas.  Largely I just wanted reusable methods to use either
the task schedule or passed in TaskRunner.  Each method is only used once
currently, but we'll need to at least add the CookieStore, and I think having
methods is less regression prone than inlinine the logic everywhere.

[mmenke, 2017/06/21 15:13:56]

Done.  I didn't do this in the first place mostly because I didn't like either
GetFile*TaskRunner as sounding awkward or Get*FileTaskRunner as interrupting
class names, and adding more works (ForFileIO or whatever) starts making these
method names absurdly long.

+  scoped_refptr<base::TaskRunner> GetTaskRunner(const base::TaskTraits& traits);
+  scoped_refptr<base::SequencedTaskRunner> GetSequencedTaskRunner(
+      const base::TaskTraits& traits);
+  scoped_refptr<base::SingleThreadTaskRunner> GetSingleThreadTaskRunner(
+      const base::TaskTraits& traits);
+
  private:
   const char* name_;
   bool enable_brotli_;
@@ -381,6 +393,7 @@ class NET_EXPORT URLRequestContextBuilder {
   bool cookie_store_set_by_client_;
 
   scoped_refptr<base::SingleThreadTaskRunner> file_task_runner_;
+
   HttpCacheParams http_cache_params_;
   HttpNetworkSession::Params http_network_session_params_;
   base::FilePath transport_security_persister_path_;