Add extensions code to use common updater in components/update_client/

extensions/browser/updater/update_client_config.cc

+// Copyright 2015 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 "extensions/browser/updater/update_client_config.h"
+
+#include "components/update_client/component_patcher_operation.h"
+#include "components/version_info/version_info.h"
+#include "content/public/browser/browser_context.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace extensions {
+
+UpdateClientConfig::UpdateClientConfig(content::BrowserContext* context)
+    : context_(context) {}
+
+int UpdateClientConfig::InitialDelay() const {

[Sorin Jianu, 2015/10/02 00:05:10]

Are the timing values for these functions correct?

[asargent_no_longer_on_chrome, 2015/10/06 21:31:17]

Maybe? In my manual tests so far they seem to have worked ok, but I haven't
looked at the code very closely to understand exactly what each one does. 

My near term plan is to only use the UpdateClient in a sort of "on demand mode",
ie only when the ExtensionUpdater has determined it wants to do a check. So I
didn't want any sort of delays introduced when calling the UpdateClient::Update
method. 

[Sorin Jianu, 2015/10/08 22:57:54]

If this is the case, then InitialDelay and NextCheckDelay are not relevant to
you, since they determine when and how often the component updater runs.

Step delay is the interval between different discrete operations that comprise
an update check: such as downloads and installs. Not relevant for our case.

OnDemandDelay is used for a cooldown period for the callers of OnDemandUpdate in
the component updater. Not relevant.

UpdateDelay is the delay between applying successive updates for components.
Could be relevant to this case, if the intention is to update more than one CRX
at a time.

My advice would be to reuse ConfiguratorImpl if possible instead of redefining
these values.

The configurator code is in general confusing, since:
* it is used at runtime to provide parameters to the code
* it is also use to inject dependencies
* it is used across several software layers: update_client and component updater
for example

I'd like to refactor this but I don't have a clear idea how and I want to avoid
proliferation of too many Configurator classes.

That said, it would be desirable to reuse the ConfiguratorImpl by composition,
if it is possible at all.

[asargent_no_longer_on_chrome, 2015/10/14 17:04:31]

Ok, I rewrote things to use a ConfiguratorImpl for most methods. However, it
wasn't clear to me that it was appropriate to include a dependency on
components/component_updater/ here in the generic extensions/ code, since
extensions in general probably should not now about the concept of binary
browser components, so I instead moved most of these methods (which mostly just
forward to ConfiguratorImpl) into the ChromeUpdateClient class. Ideally from my
perspective, ConfiguratorImpl would eventually move out of
components/component_updater/ into components/update_client/. 

[Sorin Jianu, 2015/10/14 20:37:09]

Acknowledged.

+  return 0;
+}
+
+int UpdateClientConfig::NextCheckDelay() const {
+  return 0;
+}
+
+int UpdateClientConfig::StepDelay() const {
+  return 1;
+}
+
+int UpdateClientConfig::OnDemandDelay() const {
+  return 1;
+}
+
+int UpdateClientConfig::UpdateDelay() const {
+  return 1;
+}
+
+std::string UpdateClientConfig::GetOSLongName() const {
+  return version_info::GetOSType();
+}
+
+std::string UpdateClientConfig::ExtraRequestParams() const {
+  return std::string();
+}
+
+net::URLRequestContextGetter* UpdateClientConfig::RequestContext() const {
+  if (!context_)
+    return nullptr;
+  return context_->GetRequestContext();
+}
+
+scoped_refptr<update_client::OutOfProcessPatcher>
+UpdateClientConfig::CreateOutOfProcessPatcher() const {
+  return nullptr;
+}
+
+bool UpdateClientConfig::DeltasEnabled() const {
+  return true;
+}
+
+bool UpdateClientConfig::UseBackgroundDownloader() const {
+  return false;
+}
+
+scoped_refptr<base::SequencedTaskRunner>
+UpdateClientConfig::GetSequencedTaskRunner() const {
+  return content::BrowserThread::GetBlockingPool()
+      ->GetSequencedTaskRunnerWithShutdownBehavior(
+          content::BrowserThread::GetBlockingPool()->GetSequenceToken(),
+          base::SequencedWorkerPool::SKIP_ON_SHUTDOWN);
+}
+
+scoped_refptr<base::SingleThreadTaskRunner>
+UpdateClientConfig::GetSingleThreadTaskRunner() const {
+  return content::BrowserThread::GetMessageLoopProxyForThread(
+      content::BrowserThread::FILE);
+}
+
+UpdateClientConfig::~UpdateClientConfig() {}
+
+}  // namespace extensions