mozilla-beta: changeset 319166:97c27a348f0963da5bce6b667612e7ba2d209078

☠☠ backed out by 3a53eb9e6554 ☠ ☠
author	Allasso Travesser <allassopraise@gmail.com>
	Wed, 03 Feb 2016 16:05:56 +0100
changeset 319166	97c27a348f0963da5bce6b667612e7ba2d209078
parent 319165	6826dfd0e85b29050e45273d9bfdb27dc2bc1128
child 319167	6599b14546f1a62e7089e9b8b404799db54b5da0
push id	5913
push user	jlund@mozilla.com
push date	Mon, 25 Apr 2016 16:57:49 +0000
treeherder	mozilla-beta@dcaf0a6fa115 [default view] [failures only]
perfherder	[talos] [build metrics] [platform microbench] (compared to previous push)
reviewers	dao
bugs	1241837
milestone	47.0a1
first release with	nightly linux32 03297f8c28a0 / 47.0a1 / 20160204030229 / files nightly linux64 03297f8c28a0 / 47.0a1 / 20160204030229 / files nightly mac 03297f8c28a0 / 47.0a1 / 20160204030229 / files nightly win32 03297f8c28a0 / 47.0a1 / 20160204030229 / files nightly win64 03297f8c28a0 / 47.0a1 / 20160204030229 / files
last release without	nightly linux32 f2f8fc172f4c / 47.0a1 / 20160203030249 / files nightly linux64 f2f8fc172f4c / 47.0a1 / 20160203030249 / files nightly mac f2f8fc172f4c / 47.0a1 / 20160203030249 / files nightly win32 f2f8fc172f4c / 47.0a1 / 20160203030249 / files nightly win64 f2f8fc172f4c / 47.0a1 / 20160203030249 / files

--- a/browser/base/content/tabbrowser.xml
+++ b/browser/base/content/tabbrowser.xml
@@ -1807,18 +1807,17 @@
                           Services.prefs.getBoolPref("browser.tabs.animate");
             if (!animate) {
               t.setAttribute("fadein", "true");
               setTimeout(function (tabContainer) {
                 tabContainer._handleNewTab(t);
               }, 0, this.tabContainer);
             }
 
-            // invalidate caches
-            this._browsers = null;
+            // invalidate cache
             this._visibleTabs = null;
 
             this.tabContainer.appendChild(t);
 
             // If this new tab is owned by another, assert that relationship
             if (aOwner)
               t.owner = aOwner;
 
@@ -2333,20 +2332,16 @@
             // destroyed until the document goes away.  So we force a
             // cleanup ourselves.
             // This has to happen before we remove the child so that the
             // XBL implementation of nsIObserver still works.
             browser.destroy();
 
             var wasPinned = aTab.pinned;
 
-            // Invalidate browsers cache, as the tab is removed from the
-            // tab container.
-            this._browsers = null;
-
             // Remove the tab ...
             this.tabContainer.removeChild(aTab);
 
             // ... and fix up the _tPos properties immediately.
             for (let i = aTab._tPos; i < this.tabs.length; i++)
               this.tabs[i]._tPos = i;
 
             if (!this._windowIsClosing) {
@@ -2814,25 +2809,42 @@
           ]]>
         </setter>
       </property>
 
       <property name="selectedBrowser"
                 onget="return this.mCurrentBrowser;"
                 readonly="true"/>
 
-      <property name="browsers" readonly="true">
-       <getter>
-          <![CDATA[
-            return this._browsers ||
-                   (this._browsers = Array.map(this.tabs, tab => tab.linkedBrowser));
-          ]]>
-        </getter>
-      </property>
-      <field name="_browsers">null</field>
+      <field name="browsers" readonly="true">
+        <![CDATA[
+          // This defines a proxy which allows us to access browsers by
+          // index without actually creating a full array of browsers.
+          new Proxy([], {
+            has: (target, name) => {
+              if (typeof name == "string" && Number.isInteger(parseInt(name))) {
+                return (name in this.tabs);
+              }
+              return false;
+            },
+            get: (target, name) => {
+              if (name == "length") {
+                return this.tabs.length;
+              }
+              if (typeof name == "string" && Number.isInteger(parseInt(name))) {
+                if (!(name in this.tabs)) {
+                  return undefined;
+                }
+                return this.tabs[name].linkedBrowser;
+              }
+              return target[name];
+            }
+          });
+        ]]>
+      </field>
 
       <!-- Moves a tab to a new browser window, unless it's already the only tab
            in the current window, in which case this will do nothing. -->
       <method name="replaceTabWithWindow">
         <parameter name="aTab"/>
         <parameter name="aOptions"/>
         <body>
           <![CDATA[
@@ -2883,18 +2895,17 @@
           this._lastRelatedTab = null;
 
           let wasFocused = (document.activeElement == this.mCurrentTab);
 
           aIndex = aIndex < aTab._tPos ? aIndex: aIndex+1;
           this.mCurrentTab._logicallySelected = false;
           this.mCurrentTab._visuallySelected = false;
 
-          // invalidate caches
-          this._browsers = null;
+          // invalidate cache
           this._visibleTabs = null;
 
           // use .item() instead of [] because dragging to the end of the strip goes out of
           // bounds: .item() returns null (so it acts like appendChild), but [] throws
           this.tabContainer.insertBefore(aTab, this.tabs.item(aIndex));
 
           for (let i = 0; i < this.tabs.length; i++) {
             this.tabs[i]._tPos = i;