logd: refactor chatty deduplication logging

This code and comment is hard to follow, despite the operation being
simple, so refactor the code to be easier to follow.

Also, use std::unique_ptr instead of raw pointers as appropriate.

Test: logging unit tests
Change-Id: Id1f29f4deeca730d1e3b6856e1581d0b840f883e
diff --git a/logd/LogStatistics.cpp b/logd/LogStatistics.cpp
index 14bcb63..bb7621d 100644
--- a/logd/LogStatistics.cpp
+++ b/logd/LogStatistics.cpp
@@ -79,12 +79,9 @@
 }
 }
 
-void LogStatistics::AddTotal(LogBufferElement* element) {
+void LogStatistics::AddTotal(log_id_t log_id, uint16_t size) {
     auto lock = std::lock_guard{lock_};
-    if (element->getDropped()) return;
 
-    log_id_t log_id = element->getLogId();
-    uint16_t size = element->getMsgLen();
     mSizesTotal[log_id] += size;
     SizesTotal += size;
     ++mElementsTotal[log_id];