logd: correctly label identical lines

Move lastTid array from local in LogBuffer::flushTo to per-reader
context in LogTimes::mLastTid and pass into LogBuffer::flushTo.

Replace NULL with nullptr in touched files.

Simplify LogTimeEntry::cleanSkip_Locked initialization of skipAhead
to memset, to match mLastTid memset initialization.

Test: gTest liblog-unit-tests, logd-unit-tests & logcat-unit-tests
Test: adb logcat -b all | grep chatty | grep -v identical
Bug: 36488201
Change-Id: I0c3887f220a57f80c0490be4b182657b9563aa3f
diff --git a/logd/LogTimes.cpp b/logd/LogTimes.cpp
index 04e531f..ccc550a 100644
--- a/logd/LogTimes.cpp
+++ b/logd/LogTimes.cpp
@@ -15,6 +15,7 @@
  */
 
 #include <errno.h>
+#include <string.h>
 #include <sys/prctl.h>
 
 #include <private/android_logger.h>
@@ -47,7 +48,8 @@
       mEnd(log_time(android_log_clockid())) {
     mTimeout.tv_sec = timeout / NS_PER_SEC;
     mTimeout.tv_nsec = timeout % NS_PER_SEC;
-    pthread_cond_init(&threadTriggeredCondition, NULL);
+    memset(mLastTid, 0, sizeof(mLastTid));
+    pthread_cond_init(&threadTriggeredCondition, nullptr);
     cleanSkip_Locked();
 }
 
@@ -98,7 +100,7 @@
             it++;
         }
 
-        me->mClient = NULL;
+        me->mClient = nullptr;
         reader.release(client);
     }
 
@@ -122,7 +124,7 @@
     SocketClient* client = me->mClient;
     if (!client) {
         me->error();
-        return NULL;
+        return nullptr;
     }
 
     LogBuffer& logbuf = me->mReader.logbuf();
@@ -151,12 +153,12 @@
         unlock();
 
         if (me->mTail) {
-            logbuf.flushTo(client, start, privileged, security, FilterFirstPass,
-                           me);
+            logbuf.flushTo(client, start, nullptr, privileged, security,
+                           FilterFirstPass, me);
             me->leadingDropped = true;
         }
-        start = logbuf.flushTo(client, start, privileged, security,
-                               FilterSecondPass, me);
+        start = logbuf.flushTo(client, start, me->mLastTid, privileged,
+                               security, FilterSecondPass, me);
 
         lock();
 
@@ -182,7 +184,7 @@
 
     pthread_cleanup_pop(true);
 
-    return NULL;
+    return nullptr;
 }
 
 // A first pass to count the number of elements
@@ -281,7 +283,5 @@
 }
 
 void LogTimeEntry::cleanSkip_Locked(void) {
-    for (log_id_t i = LOG_ID_MIN; i < LOG_ID_MAX; i = (log_id_t)(i + 1)) {
-        skipAhead[i] = 0;
-    }
+    memset(skipAhead, 0, sizeof(skipAhead));
 }