Downloads WebUI: move clear all toast to click handler

The clear all handler from MOJO is invoked each time search is used.
Instead of showing a toast when MOJO clear all is invoked, show the
toast in the clear all button click handler in the toolbar.

Bug: 948651
Change-Id: Ib5f1773bda8d5ffc6abe01a1e0b6f2b26450abf9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1549196
Commit-Queue: Dan Beam <dbeam@chromium.org>
Reviewed-by: Dan Beam <dbeam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#649002}

chrome/browser/resources/downloads/BUILD.gn

@@ -108,6 +108,7 @@ js_library("toolbar") {
     ":search_service",
     "//third_party/polymer/v1_0/components-chromium/iron-a11y-announcer:iron-a11y-announcer-extracted",
     "//ui/webui/resources/cr_elements/cr_action_menu:cr_action_menu",
+    "//ui/webui/resources/cr_elements/cr_toast:cr_toast_manager",
     "//ui/webui/resources/cr_elements/cr_toolbar:cr_toolbar",
     "//ui/webui/resources/js:cr",
     "//ui/webui/resources/js:util",

chrome/browser/resources/downloads/manager.js

@@ -119,8 +119,6 @@ cr.define('downloads', function() {
     /** @private */
     clearAll_: function() {
       this.set('items_', []);
-      cr.toastManager.getInstance().show(
-          loadTimeData.getString('toastClearedAll'), true);
     },
 
     /** @private */

chrome/browser/resources/downloads/toolbar.js

@@ -61,6 +61,8 @@ cr.define('downloads', function() {
       assert(this.canClearAll());
       this.mojoHandler_.clearAll();
       this.$.moreActionsMenu.close();
+      cr.toastManager.getInstance().show(
+          loadTimeData.getString('toastClearedAll'), true);
     },
 
     /** @private */