logd: validate and fill in socket credentials

- android::pidToUid() additional checking.  Make sure if we have to
  convert a PID to an UID that the parse of /proc/<pid>/status
  requires a trailing space after the number
- android::tidToPid() added, in the same vein as android::pidToUid().
- stats.tidToPid() added
- If no credentials, set PID to 0 and UID to DEFAULT_OVERFLOWUID
- If credentialed PID is 0, use stats.tidToPid()
- If credentialed UID is DEFAULT_OVERFLOWUID, use stats.pidToUid()

Test: remove +passcred from logd.rc for daemon and confirm very few
      UID=65534 or PID=0 cases actually show up
Bug: 37985222
Change-Id: I7d20506e70e67beb3043d1537cf9450ab58dc278
diff --git a/logd/LogStatistics.h b/logd/LogStatistics.h
index 945fc0a..8808aac 100644
--- a/logd/LogStatistics.h
+++ b/logd/LogStatistics.h
@@ -306,10 +306,6 @@
     std::string format(const LogStatistics& stat, log_id_t id) const;
 };
 
-namespace android {
-uid_t pidToUid(pid_t pid);
-}
-
 struct PidEntry : public EntryBaseDropped {
     const pid_t pid;
     uid_t uid;
@@ -389,6 +385,13 @@
           uid(android::pidToUid(tid)),
           name(android::tidToName(tid)) {
     }
+    TidEntry(pid_t tid)
+        : EntryBaseDropped(),
+          tid(tid),
+          pid(android::tidToPid(tid)),
+          uid(android::pidToUid(tid)),
+          name(android::tidToName(tid)) {
+    }
     explicit TidEntry(const LogBufferElement* element)
         : EntryBaseDropped(element),
           tid(element->getTid()),
@@ -785,6 +788,7 @@
     // helper (must be locked directly or implicitly by mLogElementsLock)
     const char* pidToName(pid_t pid) const;
     uid_t pidToUid(pid_t pid);
+    pid_t tidToPid(pid_t tid);
     const char* uidToName(uid_t uid) const;
 };