Manage UsbService lifetime in DeviceClient implementations.

To make it easier to reason about when the UsbService is destroyed this
patch makes its lifetime managed by the DeviceClient implementation that
created it. This means that in Chrome the UsbService is (indirectly)
owned by BrowserProcessImpl.

BUG=None
TBR=dgozman@chromium.org

Review URL: https://codereview.chromium.org/1314273002

Cr-Commit-Position: refs/heads/master@{#346264}

1 files changed, 4 insertions, 24 deletions

diff --git a/device/usb/usb_service.cc b/device/usb/usb_service.cc
index 9f9f02c2..ef6763a 100644
--- a/device/usb/usb_service.cc
+++ b/device/usb/usb_service.cc
@@ -12,12 +12,6 @@
 
 namespace device {
 
-namespace {
-
-UsbService* g_service;
-
-}  // namespace
-
 UsbService::Observer::~Observer() {}
 
 void UsbService::Observer::OnDeviceAdded(scoped_refptr<UsbDevice> device) {
@@ -31,28 +25,14 @@ void UsbService::Observer::OnDeviceRemovedCleanup(
 }
 
 // static
-UsbService* UsbService::GetInstance(
+scoped_ptr<UsbService> UsbService::Create(
     scoped_refptr<base::SequencedTaskRunner> blocking_task_runner) {
-  if (!g_service) {
-    // |g_service| is set by the UsbService constructor.
-    new UsbServiceImpl(blocking_task_runner);
-    if (!g_service) {
-      base::AtExitManager::RegisterTask(base::Bind(
-          &base::DeletePointer<UsbService>, base::Unretained(g_service)));
-    }
-  }
-  return g_service;
+  return make_scoped_ptr(new UsbServiceImpl(blocking_task_runner));
 }
 
-UsbService::UsbService() {
-  DCHECK(!g_service);
-  g_service = this;
-}
+UsbService::~UsbService() {}
 
-UsbService::~UsbService() {
-  DCHECK(g_service);
-  g_service = nullptr;
-}
+UsbService::UsbService() {}
 
 void UsbService::AddObserver(Observer* observer) {
   DCHECK(CalledOnValidThread());