[cronet] Add mechanism for restarting CronetEnvironment

components/cronet/ios/cronet_environment.mm

 // Copyright 2016 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 "components/cronet/ios/cronet_environment.h"
 
 #include <utility>
 
 #include "base/at_exit.h"
 #include "base/atomicops.h"
@@ skipping 233 matching lines @@
       this, network_io_thread_->task_runner());
   base::subtle::MemoryBarrier();
   PostToNetworkThread(FROM_HERE,
                       base::Bind(&CronetEnvironment::InitializeOnNetworkThread,
                                  base::Unretained(this)));
 }
 
 CronetEnvironment::~CronetEnvironment() {
   // net::HTTPProtocolHandlerDelegate::SetInstance(nullptr);
 
-  // TODO(lilyhoughton) right now this is relying on there being
-  // only one CronetEnvironment (per process).  if (when?) that
-  // changes, so will this have to.
-  base::TaskScheduler* ts = base::TaskScheduler::GetInstance();
-  if (ts)
-    ts->Shutdown();
+  // TODO(lilyhoughton) this can only be run once, so right now leaking it.
+  // Should be be called when the _last_ CronetEnvironment is destroyed.
+  // base::TaskScheduler* ts = base::TaskScheduler::GetInstance();
+  // if (ts)
+  //  ts->Shutdown();
+
+  // TODO(lilyhoughton) this should be smarter about making sure there are no

[mef, 2017/04/26 22:19:41]

I think there is also a problem with having objects owned by CronetEnvironment
(https://cs.chromium.org/chromium/src/components/cronet/ios/cronet_environment...)
deleted before request context.

Maybe for the purposes of this CL we should make |shutdown| a
|shutdownForTesting| and take it out of public API in Cronet.h?

[lilyhoughton, 2017/04/27 13:53:39]

Not really sure what to do about this, since afaict we can't block on waiting
for request context to be deleted on network thread?
Done.

[mef, 2017/04/27 14:58:20]

Yeah, this needs more thought and test coverage, so I think it is fine to punt
to later CL.

+  // pending requests, etc.
+
+  network_io_thread_->task_runner().get()->DeleteSoon(FROM_HERE,
+                                                      main_context_.release());
 }
 
 void CronetEnvironment::InitializeOnNetworkThread() {
   DCHECK(network_io_thread_->task_runner()->BelongsToCurrentThread());
   base::FeatureList::InitializeInstance(std::string(), std::string());
 
   static bool ssl_key_log_file_set = false;
   if (!ssl_key_log_file_set && !ssl_key_log_file_name_.empty()) {
     ssl_key_log_file_set = true;
     base::FilePath ssl_key_log_file;
@@ skipping 101 matching lines @@
   event->Signal();
 }
 
 std::string CronetEnvironment::getDefaultQuicUserAgentId() const {
   return base::SysNSStringToUTF8([[NSBundle mainBundle]
              objectForInfoDictionaryKey:@"CFBundleDisplayName"]) +
          " Cronet/" + CRONET_VERSION;
 }
 
 }  // namespace cronet