logd: statistics per-pid filter

Primarily gives access to the Chattiest TIDs and TAGs
associated with a pid.

Has a secondary effect of allowing us to pull out the
command line, comm and in some cases the associated
PACKAGE for a specific pid while the logs are still
present even if the executable is gone.

Bug: 26029733
Bug: 21615139
Change-Id: I1ea63165a680a9318360579b70b1512078ed5682
diff --git a/liblog/log_read.c b/liblog/log_read.c
index eb44b29..1aff272 100644
--- a/liblog/log_read.c
+++ b/liblog/log_read.c
@@ -501,6 +501,14 @@
         remaining -= n;
         cp += n;
     }
+
+    if (logger_list->pid) {
+        n = snprintf(cp, remaining, " pid=%u", logger_list->pid);
+        n = min(n, remaining);
+        remaining -= n;
+        cp += n;
+    }
+
     return send_log_msg(NULL, NULL, buf, len);
 }