Exposing NQE on the Browser UI thread

chrome/browser/net/nqe/ui_network_quality_estimator_service.cc

+// 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 "chrome/browser/net/nqe/ui_network_quality_estimator_service.h"
+
+#include "base/bind.h"
+#include "chrome/browser/browser_process.h"
+#include "chrome/browser/io_thread.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace chrome_browser_net {
+
+// A class that sets itself as an observer of the EffectiveconnectionType for
+// the browser IO thread. It reports any change in EffectiveConnectionType back
+// to the UI service.
+// It is created on the UI thread, but used and deleted on the IO thread.
+class UINetworkQualityEstimatorService::IONetworkQualityObserver
+    : public net::NetworkQualityEstimator::EffectiveConnectionTypeObserver {
+ public:
+  IONetworkQualityObserver(
+      base::WeakPtr<UINetworkQualityEstimatorService> service)
+      : service_(service) {
+    DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  }
+
+  ~IONetworkQualityObserver() override {
+    DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
+    if (network_quality_estimator_)
+      network_quality_estimator_->RemoveEffectiveConnectionTypeObserver(this);
+  }
+
+  void InitializeOnIOThread(IOThread* io_thread) {
+    DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
+    if (!io_thread->globals()->network_quality_estimator)
+      return;
+    network_quality_estimator_ =
+        io_thread->globals()->network_quality_estimator.get();
+    if (!network_quality_estimator_)
+      return;
+    network_quality_estimator_->AddEffectiveConnectionTypeObserver(this);
+    content::BrowserThread::PostTask(
+        content::BrowserThread::UI, FROM_HERE,
+        base::Bind(
+            &UINetworkQualityEstimatorService::EffectiveConnectionTypeChanged,
+            service_,
+            network_quality_estimator_->GetEffectiveConnectionType()));
+  }
+
+  // net::NetworkQualityEstimator::EffectiveConnectionTypeObserver
+  // implementation:
+  void OnEffectiveConnectionTypeChanged(
+      net::NetworkQualityEstimator::EffectiveConnectionType type) override {
+    DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
+    content::BrowserThread::PostTask(
+        content::BrowserThread::UI, FROM_HERE,
+        base::Bind(
+            &UINetworkQualityEstimatorService::EffectiveConnectionTypeChanged,
+            service_, type));
+  }
+
+ private:
+  base::WeakPtr<UINetworkQualityEstimatorService> service_;
+  net::NetworkQualityEstimator* network_quality_estimator_;
+
+  DISALLOW_COPY_AND_ASSIGN(IONetworkQualityObserver);
+};
+
+UINetworkQualityEstimatorService::UINetworkQualityEstimatorService(

[mmenke, 2016/07/20 17:11:33]

Are you thinking this class won't need to support its own observers, or thinking
you'll add them later?  I'm fine, either way, just curious.

[RyanSturm, 2016/07/20 17:37:38]

The current plan is to add them later.

+    Profile* profile)
+    : type_(net::NetworkQualityEstimator::EFFECTIVE_CONNECTION_TYPE_UNKNOWN),
+      io_observer_(nullptr),
+      weak_factory_(this) {
+  DCHECK(thread_checker_.CalledOnValidThread());

[mmenke, 2016/07/20 17:11:33]

optional:  Rather than a thread checks, suggest just using
DCHECK_CURRENTLY_ON(content::BrowserThread::UI);

It's a bit more explicit.

[RyanSturm, 2016/07/20 17:37:38]

sgtm.

+  io_observer_ = new IONetworkQualityObserver(weak_factory_.GetWeakPtr());
+  content::BrowserThread::PostTask(
+      content::BrowserThread::IO, FROM_HERE,
+      base::Bind(&IONetworkQualityObserver::InitializeOnIOThread,
+                 base::Unretained(io_observer_),
+                 g_browser_process->io_thread()));
+}
+
+UINetworkQualityEstimatorService::~UINetworkQualityEstimatorService() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+}
+
+void UINetworkQualityEstimatorService::Shutdown() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  weak_factory_.InvalidateWeakPtrs();
+}
+
+void UINetworkQualityEstimatorService::EffectiveConnectionTypeChanged(
+    net::NetworkQualityEstimator::EffectiveConnectionType type) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  type_ = type;
+}
+
+net::NetworkQualityEstimator::EffectiveConnectionType
+UINetworkQualityEstimatorService::GetEffectiveConnectionType() const {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  return type_;
+}
+
+}  // namespace chrome_browser_net