Bug 1496685 - Implement UrlbarController::viewContextChanged. r=dao

Differential Revision: https://phabricator.services.mozilla.com/D20841

--HG--
extra : moz-landing-system : lando

browser/components/urlbar/UrlbarController.jsm

@@ -92,9 +92,8 @@ class UrlbarController {
    */
   async startQuery(queryContext) {
     // Cancel any running query.
-    if (this._lastQueryContext) {
-      this.cancelQuery(this._lastQueryContext);
-    }
+    this.cancelQuery();
+
     this._lastQueryContext = queryContext;
 
     queryContext.lastResultCount = 0;
@@ -174,11 +173,14 @@ class UrlbarController {
   }
 
   /**
-   * When switching tabs, clear some internal caches to handle cases like
-   * backspace, autofill or repeated searches.
+   * When the containing context changes (for example when switching tabs),
+   * clear any caches that connects consecutive searches in the same context.
+   * For example it can be used to clear information used to improve autofill
+   * or save resourced on repeated searches.
    */
-  tabContextChanged() {
-    // TODO: implementation needed (bug 1496685)
+  viewContextChanged() {
+    this.cancelQuery();
+    this._notify("onViewContextChanged");
   }
 
   /**

browser/components/urlbar/UrlbarInput.jsm

@@ -1107,7 +1107,7 @@ class UrlbarInput {
   }
 
   _on_TabSelect(event) {
-    this.controller.tabContextChanged();
+    this.controller.viewContextChanged();
   }
 
   _on_keydown(event) {

browser/components/urlbar/UrlbarView.jsm

@@ -272,6 +272,16 @@ class UrlbarView {
     }
   }
 
+  /**
+   * Notified when the view context changes, for example when switching tabs.
+   * It can be used to reset internal state tracking.
+   */
+  onViewContextChanged() {
+    // Clear rows, so that when reusing results we don't visually leak them
+    // across different contexts.
+    this._rows.textContent = "";
+  }
+
   /**
    * Passes DOM events for the view to the _on_<event type> methods.
    * @param {Event} event

browser/docs/AddressBar.rst

@@ -259,9 +259,9 @@ View (e.g. showing/hiding a panel). It is also responsible for reporting Telemet
     // Used by the View to listen for results.
     addQueryListener(listener);
     removeQueryListener(listener);
-    // Used to indicate the View context changed, as such any cached information
-    // should be reset.
-    tabContextChanged();
+    // Used to indicate the View context changed, so that cached information
+    // about the latest search is no more relevant and can be dropped.
+    viewContextChanged();
   }
 
 
@@ -347,8 +347,12 @@ Represents the base *View* implementation, communicates with the *Controller*.
     onQueryCancelled(queryContext);
     // Invoked when the query is done.
     onQueryFinished(queryContext);
+    // Invoked when the view context changed, so that cached information about
+    // the latest search is no more relevant and can be dropped.
+    onViewContextChanged();
   }
 
+
 UrlbarResult
 ===========
 
@@ -399,6 +403,7 @@ The following RESULT_TYPEs are supported:
     // Payload: { icon, url, device, title }
     REMOTE_TAB: 6,
 
+
 Shared Modules
 ==============