Visualize CPU time versus wall time for thread slices.

Thread slices now have a highlighted section to show how much of the
duration represents CPU time (darker) and how much represents wall
time (dark + lighter).

Bug: 141530588
Change-Id: I1c61cdb62e599b5782c2a91ca2da869f787e7a72
diff --git a/CHANGELOG b/CHANGELOG
index ff0a59d..a44b463 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -4,7 +4,8 @@
   Trace Processor:
     *
   UI:
-    *
+    * Added a highlighted section to thread slices to visualize CPU time 
+      (darker) verses wall time (lighter).
   SDK:
     *