Revert of [Devtools] Fix network timeline canvas selection splitview …

…(patchset #1 id:1 of https://codereview.chromium.org/2465373002/ )

Reason for revert:
I'll reapply it.

Original issue's description:
> [Devtools] Fix network timeline canvas selection splitview
>
> This patch fixes a regression caused when a user selects a request
> in the new network canvas timeline it would show the canvas to the left
> instead of the name column.
>
> R=dgozman
> BUG=653738

[email protected],[email protected]
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=653738

Review-Url: https://codereview.chromium.org/2472523002
Cr-Commit-Position: refs/heads/master@{#429097}

front_end/network/NetworkLogViewColumns.js

@@ -759,7 +759,7 @@ WebInspector.NetworkLogViewColumns.prototype = {
             this._dataGridScroller.style.overflow = "hidden";
             this._dataGrid.setScrollContainer(this._timelineScroller);
         } else {
-            this._splitWidget.hideSidebar();
+            this._splitWidget.hideMain();
             this._activeScroller = this._dataGridScroller;
             this._dataGridScroller.style.overflow = "overlay";
             this._dataGrid.setScrollContainer(this._dataGridScroller);