Add GamepadService, owns 1 gamepad bg thread

content/browser/gamepad/gamepad_service.cc

+// Copyright (c) 2011 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 "content/browser/gamepad/gamepad_service.h"
+
+#include "content/browser/gamepad/data_fetcher.h"
+#include "content/browser/gamepad/gamepad_provider.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/notification_service.h"
+#include "content/public/browser/notification_source.h"
+#include "content/public/browser/notification_types.h"
+#include "content/public/browser/render_process_host.h"
+
+namespace content {
+
+GamepadService* GamepadService::instance_;
+
+GamepadService::GamepadService() : num_readers_(0) {
+}
+
+GamepadService::~GamepadService() {
+}
+
+GamepadService* GamepadService::GetInstance() {
+  if (!instance_) {
+    instance_ = new GamepadService();

[jam, 2011/12/01 20:07:31]

just use Singleton for singletons :)

[scottmg, 2011/12/01 22:05:32]

Done. (was because of the refcount cruft which is fixed now)

+    instance_->AddRef();
+  }
+  return instance_;
+}
+
+void GamepadService::Start(
+    GamepadDataFetcher* data_fetcher,
+    content::RenderProcessHost* associated_rph) {
+  num_readers_++;
+  if (!provider_)
+    provider_ = new GamepadProvider(data_fetcher);
+  DCHECK(num_readers_ > 0);
+  provider_->Resume();
+
+  content::BrowserThread::PostTask(
+      content::BrowserThread::UI,
+      FROM_HERE,
+      base::Bind(&GamepadService::RegisterForCloseNotification,
+                 this,
+                 associated_rph));
+}
+
+void GamepadService::RegisterForCloseNotification(
+    content::RenderProcessHost* rph) {
+  registrar_.Add(this,
+                 content::NOTIFICATION_RENDERER_PROCESS_CLOSED,
+                 content::Source<content::RenderProcessHost>(rph));
+}
+
+base::SharedMemoryHandle GamepadService::GetSharedMemoryHandle(
+    base::ProcessHandle handle) {
+  DCHECK(provider_);

[jam, 2011/12/01 20:07:31]

nit: by convention we avoid DCHECKing variables before using them. in release
builds, this does nothing. in debug, the crash in the following line is just as
good

[scottmg, 2011/12/01 22:05:32]

Done.

+  return provider_->GetRendererSharedMemoryHandle(handle);
+}
+
+void GamepadService::Stop() {
+  --num_readers_;
+  DCHECK(provider_);

[jam, 2011/12/01 20:07:31]

ditto

[scottmg, 2011/12/01 22:05:32]

Done.

+  DCHECK(num_readers_ >= 0);
+
+  if (num_readers_ == 0)
+    provider_->Pause();
+}
+
+void GamepadService::Observe(int type,
+    const content::NotificationSource& source,
+    const content::NotificationDetails& details) {
+  switch (type) {

[jam, 2011/12/01 20:07:31]

nit: just do line 77-80 only since you're registering for one notification

[scottmg, 2011/12/01 22:05:32]

Done.

+    case content::NOTIFICATION_RENDERER_PROCESS_CLOSED: {
+      content::BrowserThread::PostTask(
+          content::BrowserThread::IO,
+          FROM_HERE,
+          base::Bind(&GamepadService::Stop, this));
+      break;
+    }
+    default: {
+      break;
+    }
+  }
+}
+
+} // namespace content