DevTools: allow hiding threads sidebar via module configuration.

Change-Id: I43c98ef335c76b0bbc5276742fdfe791c40f3a7d
Reviewed-on: https://chromium-review.googlesource.com/c/1357009Reviewed-by: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612758}

third_party/blink/renderer/devtools/front_end/sources/SourcesPanel.js

@@ -177,14 +177,13 @@ Sources.SourcesPanel = class extends UI.Panel {
   _showThreadsIfNeeded() {
     if (Sources.ThreadsSidebarPane.shouldBeShown() && !this._threadsSidebarPane) {
       this._threadsSidebarPane = /** @type {!UI.View} */ (UI.viewManager.view('sources.threads'));
-      if (this._sidebarPaneStack) {
+      if (this._sidebarPaneStack && this._threadsSidebarPane) {
         this._sidebarPaneStack.showView(
             this._threadsSidebarPane, this._splitWidget.isVertical() ? this._watchSidebarPane : this._callstackPane);
       }
     }
   }
 
-
   /**
    * @param {?SDK.Target} target
    */

third_party/blink/renderer/devtools/front_end/sources/module.json

@@ -728,7 +728,8 @@
             "id": "sources.threads",
             "title": "Threads",
             "persistence": "permanent",
-            "className": "Sources.ThreadsSidebarPane"
+            "className": "Sources.ThreadsSidebarPane",
+            "condition": "!sources.hide_thread_sidebar"
         },
         {
             "type": "view",