liblog: Support for ANDROID_LOG_WRAP mode flag on reader

If ANDROID_LOG_WRAP is specified, add timeout=3600 to the reader
request. logd will comply by going to sleep with the socket open.
If the start time is about to wrap or get pruned in the specified log
buffers, then wakeup and dump the logs; or wakeup on timeout,
whichever comes first.

Bug: 25929746
Change-Id: I531b4317a20abcf3ba87d78c68fa2f268a4488ab
diff --git a/liblog/README b/liblog/README
index f29ac04..df1e68c 100644
--- a/liblog/README
+++ b/liblog/README
@@ -116,6 +116,10 @@
        code,  otherwise the  android_logger_list_read  call will block for new
        entries.
 
+       The  ANDROID_LOG_WRAP  mode flag to the  android_logger_list_alloc_time
+       signals  logd to quiesce  the reader until the buffer is about to prune
+       at the start time then proceed to dumping content.
+
        The  ANDROID_LOG_PSTORE mode flag to the android_logger_open is used to
        switch from the active logs to the persistent logs from before the last
        reboot.