dbus-vis: Fix "display row" upper bound

In this affected line, j should go up to "number of visual lines"
minus 1. This can be more than "this.Intervals.length" due to the
headers.

Signed-off-by: Sui Chen <suichen@google.com>
Change-Id: I34b5975fb1b06393427397f7f1d165305243b35a
diff --git a/dbus-vis/timeline_view.js b/dbus-vis/timeline_view.js
index 3ef81da..2971ec6 100644
--- a/dbus-vis/timeline_view.js
+++ b/dbus-vis/timeline_view.js
@@ -1263,7 +1263,7 @@
       // 2. an actual row of data (in the Intervals variable)
 
       // 'j' needs to go PAST the viewport if the last row is overlapping and spans beyond the viewport.
-      for (let j = j0; j < this.Intervals.length; j++) {
+      for (let j = j0; j < tvh; j++) {
 
         if (j >= this.VisualLineStartIdx) { should_render = true; }
         if (y > height) { should_render = false; }