Add static method to allow creating global SystemNetworkContextManager on demand

When running network service without launching full browser process,
ChromeContentBrowserClient::OnNetworkServiceCreated() will be called
without g_browser_process. This CL allows us to create
SystemNetworkContextManager on demand and services depending on the
network service can call SystemNetworkContextManager::GetInstance()
to access it.

BUG=866028

Change-Id: I9a557921e1bb164ecd62c766dd698137498c0a47
Reviewed-on: https://chromium-review.googlesource.com/1256207
Commit-Queue: Min Qin <qinmin@chromium.org>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#596269}

chrome/browser/browser_process_impl.cc

@@ -440,7 +440,7 @@ void BrowserProcessImpl::StartTearDown() {
     local_state_->CommitPendingWrite();
 
   // This expects to be destroyed before the task scheduler is torn down.
-  system_network_context_manager_.reset();
+  SystemNetworkContextManager::DeleteInstance();
 }
 
 void BrowserProcessImpl::PostDestroyThreads() {
@@ -643,8 +643,8 @@ IOThread* BrowserProcessImpl::io_thread() {
 SystemNetworkContextManager*
 BrowserProcessImpl::system_network_context_manager() {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
-  DCHECK(system_network_context_manager_.get());
-  return system_network_context_manager_.get();
+  DCHECK(SystemNetworkContextManager::GetInstance());
+  return SystemNetworkContextManager::GetInstance();
 }
 
 scoped_refptr<network::SharedURLLoaderFactory>
@@ -1173,12 +1173,12 @@ void BrowserProcessImpl::PreCreateThreads(
   // Must be created before the IOThread.
   // TODO(mmenke): Once IOThread class is no longer needed (not the thread
   // itself), this can be created on first use.
-  system_network_context_manager_ =
-      std::make_unique<SystemNetworkContextManager>(local_state_.get());
+  if (!SystemNetworkContextManager::GetInstance())
+    SystemNetworkContextManager::CreateInstance(local_state_.get());
   io_thread_ = std::make_unique<IOThread>(
       local_state(), policy_service(), net_log_.get(),
       extension_event_router_forwarder(),
-      system_network_context_manager_.get());
+      SystemNetworkContextManager::GetInstance());
 }
 
 void BrowserProcessImpl::PreMainMessageLoopRun() {

chrome/browser/browser_process_impl.h

@@ -133,6 +133,8 @@ class BrowserProcessImpl : public BrowserProcess,
   metrics::MetricsService* metrics_service() override;
   rappor::RapporServiceImpl* rappor_service() override;
   IOThread* io_thread() override;
+  // TODO(qinmin): Remove this method as callers can retrieve the global
+  // instance from SystemNetworkContextManager directly.
   SystemNetworkContextManager* system_network_context_manager() override;
   scoped_refptr<network::SharedURLLoaderFactory> shared_url_loader_factory()
       override;
@@ -256,8 +258,6 @@ class BrowserProcessImpl : public BrowserProcess,
 
   std::unique_ptr<PrefService> local_state_;
 
-  std::unique_ptr<SystemNetworkContextManager> system_network_context_manager_;
-
   std::unique_ptr<network::NetworkQualityTracker> network_quality_tracker_;
 
   // Listens to NetworkQualityTracker and sends network quality updates to the

chrome/browser/chrome_content_browser_client.cc

@@ -4583,8 +4583,16 @@ void ChromeContentBrowserClient::WillCreateWebSocket(
 
 void ChromeContentBrowserClient::OnNetworkServiceCreated(
     network::mojom::NetworkService* network_service) {
+  if (!base::FeatureList::IsEnabled(network::features::kNetworkService))
+    return;
+  if (!SystemNetworkContextManager::GetInstance()) {
+    DCHECK(!g_browser_process);
+    DCHECK(chrome_feature_list_creator_->simple_local_state());
+    SystemNetworkContextManager::CreateInstance(
+        chrome_feature_list_creator_->simple_local_state());
+  }
   // Need to set up global NetworkService state before anything else uses it.
-  g_browser_process->system_network_context_manager()->OnNetworkServiceCreated(
+  SystemNetworkContextManager::GetInstance()->OnNetworkServiceCreated(
       network_service);
 }
 

chrome/browser/chrome_feature_list_creator.h

@@ -28,6 +28,8 @@ class ChromeFeatureListCreator {
 
   void CreatePrefServiceForTesting();
 
+  PrefService* simple_local_state() { return simple_local_state_.get(); }
+
  private:
   void CreatePrefService();
 

chrome/browser/net/system_network_context_manager.cc

@@ -10,7 +10,6 @@
 
 #include "base/command_line.h"
 #include "base/feature_list.h"
-#include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/metrics/field_trial_params.h"
 #include "base/process/process_handle.h"
@@ -75,6 +74,9 @@
 
 namespace {
 
+// The global instance of the SystemNetworkContextmanager.
+SystemNetworkContextManager* g_system_network_context_manager = nullptr;
+
 // Called on IOThread to disable QUIC for HttpNetworkSessions not using the
 // network service. Note that re-enabling QUIC dynamically is not supported for
 // simpliciy and requires a browser restart.
@@ -223,9 +225,6 @@ bool ShouldEnableAsyncDns() {
 
 }  // namespace
 
-base::LazyInstance<SystemNetworkContextManager>::Leaky
-    g_system_network_context_manager = LAZY_INSTANCE_INITIALIZER;
-
 // SharedURLLoaderFactory backed by a SystemNetworkContextManager and its
 // network context. Transparently handles crashes.
 class SystemNetworkContextManager::URLLoaderFactoryForSystem
@@ -342,6 +341,26 @@ void SystemNetworkContextManager::SetUp(
                         dns_over_https_servers);
 }
 
+// static
+SystemNetworkContextManager* SystemNetworkContextManager::CreateInstance(
+    PrefService* pref_service) {
+  DCHECK(!g_system_network_context_manager);
+  g_system_network_context_manager =
+      new SystemNetworkContextManager(pref_service);
+  return g_system_network_context_manager;
+}
+
+// static
+SystemNetworkContextManager* SystemNetworkContextManager::GetInstance() {
+  return g_system_network_context_manager;
+}
+
+// static
+void SystemNetworkContextManager::DeleteInstance() {
+  DCHECK(g_system_network_context_manager);
+  delete g_system_network_context_manager;
+}
+
 SystemNetworkContextManager::SystemNetworkContextManager(
     PrefService* local_state)
     : local_state_(local_state),

chrome/browser/net/system_network_context_manager.h

@@ -49,10 +49,18 @@ class SharedURLLoaderFactory;
 // to being compatible with the network service.
 class SystemNetworkContextManager {
  public:
-  // Constructor. |pref_service| must out live this object.
-  explicit SystemNetworkContextManager(PrefService* pref_service);
   ~SystemNetworkContextManager();
 
+  // Creates the global instance of SystemNetworkContextManager. If an
+  // instance already exists, this will cause a DCHECK failure.
+  static SystemNetworkContextManager* CreateInstance(PrefService* pref_service);
+
+  // Gets the global SystemNetworkContextManager instance.
+  static SystemNetworkContextManager* GetInstance();
+
+  // Destroys the global SystemNetworkContextManager instance.
+  static void DeleteInstance();
+
   static void RegisterPrefs(PrefRegistrySimple* registry);
 
   // Initializes |network_context_params| as needed to set up a system
@@ -140,6 +148,9 @@ class SystemNetworkContextManager {
  private:
   class URLLoaderFactoryForSystem;
 
+  // Constructor. |pref_service| must out live this object.
+  explicit SystemNetworkContextManager(PrefService* pref_service);
+
   void UpdateReferrersEnabled();
 
   // Creates parameters for the NetworkContext. May only be called once, since