Fix link error of PROCESS_STATE_NONEXISTENT.

* A reference to PROCESS_STATE_NONEXISTENT will cause link error with
  clang or standard C++ compiler because there is no out-of-class definition,
  although g++ is allowing it.
  Use +PROCESS_STATE_NONEXISTENT to get the value instead of reference.

Change-Id: I62049584b94e6847b64b572f6ef6c3e9dcc573eb
diff --git a/services/camera/libcameraservice/CameraService.cpp b/services/camera/libcameraservice/CameraService.cpp
index 574165b..55f7a40 100644
--- a/services/camera/libcameraservice/CameraService.cpp
+++ b/services/camera/libcameraservice/CameraService.cpp
@@ -884,7 +884,11 @@
         std::vector<int> ownerPids(mActiveClientManager.getAllOwners());
         ownerPids.push_back(clientPid);
 
-        std::vector<int> priorities(ownerPids.size(), PROCESS_STATE_NONEXISTENT);
+        // Use the value +PROCESS_STATE_NONEXISTENT, to avoid taking
+        // address of PROCESS_STATE_NONEXISTENT as a reference argument
+        // for the vector constructor. PROCESS_STATE_NONEXISTENT does
+        // not have an out-of-class definition.
+        std::vector<int> priorities(ownerPids.size(), +PROCESS_STATE_NONEXISTENT);
 
         // Get priorites of all active PIDs
         ProcessInfoService::getProcessStatesFromPids(ownerPids.size(), &ownerPids[0],