dbus-vis: Use IPC for open file dialog

Previously, the "open file" dialog is opened in the renderer thread
running "initialization.js".

This change moves the dialog to the main thread (main.js) so that the
renderer thread emits a "file-request" request and the main thread
answers with a "filename" response.

This IPC paradigm is required for newer versions of Electron, because
the "dialog" module cannot be imported in renderer threads in those
newer versions.

Signed-off-by: Sui Chen <suichen@google.com>
Change-Id: Ifd324688bb8a4dbdc6a5f86082fb3d205af0d77a
diff --git a/dbus-vis/ipmi_timeline_vis.js b/dbus-vis/ipmi_timeline_vis.js
index 0b3aa74..fd7ec03 100644
--- a/dbus-vis/ipmi_timeline_vis.js
+++ b/dbus-vis/ipmi_timeline_vis.js
@@ -13,7 +13,7 @@
 //    picks up the updated Intervals and Titles arrays and draws on the canvas
 //    accordingly.
 
-const {dialog} = require('electron').remote;
+const {dialog} = require('electron');
 const {fs} = require('file-system');
 const {util} = require('util');
 const {exec} = require('child_process');