logd: move current sequence from LogBufferElement to LogBuffer

This is required for tests that are aware of sequence numbers to pass;
each new LogBuffer instance should start from sequence = 1, which
isn't the case if the current sequence number is a static.

Test: unit tests
Change-Id: Ie488f8ac5e22b946b7e6237d1d5caf14929c0ec3
diff --git a/logd/LogBufferElement.cpp b/logd/LogBufferElement.cpp
index 3bcf11d..c6dbda8 100644
--- a/logd/LogBufferElement.cpp
+++ b/logd/LogBufferElement.cpp
@@ -30,14 +30,12 @@
 #include "LogStatistics.h"
 #include "LogUtils.h"
 
-atomic_int_fast64_t LogBufferElement::sequence(1);
-
 LogBufferElement::LogBufferElement(log_id_t log_id, log_time realtime, uid_t uid, pid_t pid,
-                                   pid_t tid, const char* msg, uint16_t len)
+                                   pid_t tid, uint64_t sequence, const char* msg, uint16_t len)
     : mUid(uid),
       mPid(pid),
       mTid(tid),
-      mSequence(sequence.fetch_add(1, memory_order_relaxed)),
+      mSequence(sequence),
       mRealTime(realtime),
       mMsgLen(len),
       mLogId(log_id),