Fix potential crashes in NetworkHandler code

chromeos/network/network_state_handler.cc

Index: chromeos/network/network_state_handler.cc
diff --git a/chromeos/network/network_state_handler.cc b/chromeos/network/network_state_handler.cc
index 5f4738a6cdfa0335e61aa025d72dfdf589114e36..f18ffabfc19eff60d251db6e2e9bb6216679c515 100644
--- a/chromeos/network/network_state_handler.cc
+++ b/chromeos/network/network_state_handler.cc
@@ -92,20 +92,22 @@ void NetworkStateHandler::AddObserver(
     NetworkStateHandlerObserver* observer,
     const tracked_objects::Location& from_here) {
   observers_.AddObserver(observer);
-  device_event_log::AddEntry(from_here.file_name(), from_here.line_number(),
-                             device_event_log::LOG_TYPE_NETWORK,
-                             device_event_log::LOG_LEVEL_DEBUG,
-                             "NetworkStateHandler::AddObserver");
+  device_event_log::AddEntry(
+      from_here.file_name(), from_here.line_number(),
+      device_event_log::LOG_TYPE_NETWORK, device_event_log::LOG_LEVEL_DEBUG,
+      base::StringPrintf("NetworkStateHandler::AddObserver: 0x%lx",
+                         (int64_t)observer));

[oshima, 2016/01/05 23:14:36]

%p ? (or static_cast<>)

[stevenjb, 2016/01/06 00:43:04]

Done.

 }
 
 void NetworkStateHandler::RemoveObserver(
     NetworkStateHandlerObserver* observer,
     const tracked_objects::Location& from_here) {
   observers_.RemoveObserver(observer);
-  device_event_log::AddEntry(from_here.file_name(), from_here.line_number(),
-                             device_event_log::LOG_TYPE_NETWORK,
-                             device_event_log::LOG_LEVEL_DEBUG,
-                             "NetworkStateHandler::RemoveObserver");
+  device_event_log::AddEntry(
+      from_here.file_name(), from_here.line_number(),
+      device_event_log::LOG_TYPE_NETWORK, device_event_log::LOG_LEVEL_DEBUG,
+      base::StringPrintf("NetworkStateHandler::RemoveObserver: 0x%lx",
+                         (int64_t)observer));

[oshima, 2016/01/05 23:14:36]

ditto

[stevenjb, 2016/01/06 00:43:04]

Done.

 }
 
 NetworkStateHandler::TechnologyState NetworkStateHandler::GetTechnologyState(