logd: replace stats.add+stats.subtract with stats.addTotal

Replace stats.add(elem) + stats.subtract(elem) with a new more
efficient method stats.addTotal(elem).

Test: gTest liblog-unit-test, logd-unit-tests and logcat-unit-tests
Bug: 37254265
Change-Id: I2b3c2ac44209772b38f383ae46fe6c4422b542cf
diff --git a/logd/LogStatistics.h b/logd/LogStatistics.h
index 066b7de..e171e4a 100644
--- a/logd/LogStatistics.h
+++ b/logd/LogStatistics.h
@@ -576,6 +576,7 @@
         enable = true;
     }
 
+    void addTotal(LogBufferElement* entry);
     void add(LogBufferElement* entry);
     void subtract(LogBufferElement* entry);
     // entry->setDropped(1) must follow this call