logd: oneline statistics does not report PID gone

- oneline, add check for gone
- Add pidGone() method, which caches the gone status

Change-Id: I8f03daeafb58583c2b08ec6b540486c05da0872d
diff --git a/logd/LogStatistics.h b/logd/LogStatistics.h
index cd6ef7b..3733137 100644
--- a/logd/LogStatistics.h
+++ b/logd/LogStatistics.h
@@ -37,6 +37,7 @@
     size_t mElements;
 
     char *name;
+    bool mGone;
 
 public:
     static const pid_t gone = (pid_t) -1;
@@ -46,6 +47,7 @@
     ~PidStatistics();
 
     pid_t getPid() const { return pid; }
+    bool pidGone();
     char *getName() const { return name; }
     void setName(char *name);