[Proximity Auth] Create one ProximityAuthClient per profile, rather than one global one.

components/proximity_auth/screenlock_bridge.cc

Index: components/proximity_auth/screenlock_bridge.cc
diff --git a/components/proximity_auth/screenlock_bridge.cc b/components/proximity_auth/screenlock_bridge.cc
index 2af83781dc0dfe986a4ffb3114cf1781361ab2ce..9d70799735e94df0a185bd06a942adea49e98921 100644
--- a/components/proximity_auth/screenlock_bridge.cc
+++ b/components/proximity_auth/screenlock_bridge.cc
@@ -49,9 +49,7 @@ std::string GetIdForIcon(ScreenlockBridge::UserPodCustomIcon icon) {
 
 }  // namespace
 
-ScreenlockBridge::ScreenlockBridge(ProximityAuthClient* client)
-    : client_(client), lock_handler_(nullptr) {
-  DCHECK(client_);
+ScreenlockBridge::ScreenlockBridge() : lock_handler_(nullptr) {
 }
 
 ScreenlockBridge::~ScreenlockBridge() {
@@ -150,19 +148,19 @@ bool ScreenlockBridge::IsLocked() const {
   return lock_handler_ != nullptr;
 }
 
-void ScreenlockBridge::Lock(content::BrowserContext* browser_context) {
+void ScreenlockBridge::Lock(ProximityAuthClient* client) {

[Tim Song, 2015/06/26 23:46:43]

Hmm... requiring the client here couples the ScreenlockBridge really tightly
with proximity_auth. I wonder if its worth having the Lock() and Unlock()
methods at all, since they only seem to be used in a small number of places.

[Ilya Sherman, 2015/06/27 08:18:00]

I removed the Lock() implementation for now, since we aren't actually using this
class on non-ChromeOS platforms for now... and we'd probably prefer to lock the
screen -- rather than Chrome -- on the other platforms anyway.

 #if defined(OS_CHROMEOS)
   chromeos::SessionManagerClient* session_manager =
       chromeos::DBusThreadManager::Get()->GetSessionManagerClient();
   session_manager->RequestLockScreen();
 #else
-  client_->Lock(browser_context);
+  client->Lock();
 #endif
 }
 
-void ScreenlockBridge::Unlock(content::BrowserContext* browser_context) {
+void ScreenlockBridge::Unlock(ProximityAuthClient* client) {

[Tim Song, 2015/06/26 23:46:43]

I think it would be better to take the username directly as an argument.

[Ilya Sherman, 2015/06/27 08:18:00]

Done.

   if (lock_handler_)
-    lock_handler_->Unlock(client_->GetAuthenticatedUsername(browser_context));
+    lock_handler_->Unlock(client->GetAuthenticatedUsername());
 }
 
 void ScreenlockBridge::AddObserver(Observer* observer) {