Remove the file thread dependency from FileNetLogObserver.

components/cronet/android/cronet_library_loader.cc

 // Copyright 2014 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/android/cronet_library_loader.h"
 
 #include <jni.h>
 #include <vector>
 
 #include "base/android/base_jni_onload.h"
 #include "base/android/base_jni_registrar.h"
 #include "base/android/jni_android.h"
 #include "base/android/jni_registrar.h"
 #include "base/android/jni_utils.h"
 #include "base/android/library_loader/library_loader_hooks.h"
 #include "base/feature_list.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/statistics_recorder.h"
+#include "base/task_scheduler/task_scheduler.h"
 #include "components/cronet/android/cronet_bidirectional_stream_adapter.h"
 #include "components/cronet/android/cronet_jni_registration.h"
 #include "components/cronet/android/cronet_upload_data_stream_adapter.h"
 #include "components/cronet/android/cronet_url_request_adapter.h"
 #include "components/cronet/android/cronet_url_request_context_adapter.h"
 #include "components/cronet/version.h"
 #include "jni/CronetLibraryLoader_jni.h"
 #include "net/android/net_jni_registrar.h"
 #include "net/android/network_change_notifier_factory_android.h"
 #include "net/base/network_change_notifier.h"
@@ skipping 29 matching lines @@
 net::NetworkChangeNotifier* g_network_change_notifier = nullptr;
 
 bool RegisterJNI(JNIEnv* env) {
   return base::android::RegisterNativeMethods(
       env, kCronetRegisteredMethods, arraysize(kCronetRegisteredMethods));
 }
 
 bool NativeInit() {
   if (!base::android::OnJNIOnLoadInit())
     return false;
+  base::TaskScheduler::CreateAndStartWithDefaultParams("Cronet");

[mmenke, 2017/07/06 01:50:01]

I don't think we want to create another thread in Cronet.

[mmenke, 2017/07/06 15:22:26]

I think we'll need to talk about the Cronet folks about what to do here, if we
want to use the task scheduler on Cronet at all - it looks like there's no way
to tell the task scheduler to only use 1 or 2 threads total.  Instead, we tell
it the max number of threads of each type, for 4 different thread types, meaning
a minimum of 4 threads (Though it can stop them when idle).

[mef, 2017/07/06 19:53:01]

Good point. 
I didn't realize that base::TaskScheduler::CreateAndStartWithDefaultParams()
creates a bunch of threads. 
It seems like a way of the future though, right? 
Maybe Cronet should create task scheduler with custom params?

+
   url::Initialize();
   // Initializes the statistics recorder system. This needs to be done before
   // emitting histograms to prevent memory leaks (crbug.com/707836).
   base::StatisticsRecorder::Initialize();
   return true;
 }
 
 }  // namespace
 
 bool OnInitThread() {
@@ skipping 10 matching lines @@
   }
   // TODO(agrieve): Delete this block, this is a no-op now.
   // https://crbug.com/683256.
   if (!RegisterJNI(env) || !NativeInit()) {
     return -1;
   }
   return JNI_VERSION_1_6;
 }
 
 void CronetOnUnLoad(JavaVM* jvm, void* reserved) {
+  if (base::TaskScheduler::GetInstance())
+    base::TaskScheduler::GetInstance()->Shutdown();
+
   base::android::LibraryLoaderExitHook();
 }
 
 void CronetInitOnInitThread(JNIEnv* env, const JavaParamRef<jclass>& jcaller) {
 #if !BUILDFLAG(USE_PLATFORM_ICU_ALTERNATIVES)
   base::i18n::InitializeICU();
 #endif
 
   base::FeatureList::InitializeInstance(std::string(), std::string());
   DCHECK(!base::MessageLoop::current());
   DCHECK(!g_init_message_loop);
   g_init_message_loop =
       new base::MessageLoop(base::MessageLoop::Type::TYPE_JAVA);
   static_cast<base::MessageLoopForUI*>(g_init_message_loop)->Start();
   DCHECK(!g_network_change_notifier);
   net::NetworkChangeNotifier::SetFactory(
       new net::NetworkChangeNotifierFactoryAndroid());
   g_network_change_notifier = net::NetworkChangeNotifier::Create();
 }
 
 ScopedJavaLocalRef<jstring> GetCronetVersion(
     JNIEnv* env,
     const JavaParamRef<jclass>& jcaller) {
   return base::android::ConvertUTF8ToJavaString(env, CRONET_VERSION);
 }
 
 }  // namespace cronet