tp: support multiple queries being passed to ExecuteQuery

This CL adds support for multiple semi-colon delimited queries being
passed to ExecuteQuery; all the queries will be run with the final one
being iterable using the Iterator.

Change-Id: I7c27ae03ac2296e3b557102570c432820cef8b8c
Bug: 205575589

CHANGELOG

diff --git a/CHANGELOG b/CHANGELOG
index 26e0f58..8a10c54 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -3,7 +3,11 @@
     * Changed output format of perfetto --query. Made the output more compact
       and added a summary of ongoing tracing sessions for the caller UID.
   Trace Processor:
-    *
+    * Add support for multiple SQL statements to be passed to
+      TraceProcessor::ExecuteQuery. All queries will be executed fully, with
+      the returned iterator yielding rows for the final statement.
+    * Add support for multi-line SQL comments; previously only single line
+      comments were supported.
   UI:
     *
   SDK: