Bug 1483363: Stop loading ZoomChild.jsm before necessary. r=mconley

--HG--
extra : rebase_source : 0145f5c1cded4b38f65570b75710d98370da3a32
extra : amend_source : dd6b99a67ffd22b439544295d6e16a8deb0d6dd8

browser/base/content/test/performance/browser_startup_content.js

@@ -59,7 +59,6 @@ const whitelist = {
     "resource://gre/modules/PrivateBrowsingUtils.jsm",
     "resource://gre/modules/ReaderMode.jsm",
     "resource://gre/modules/WebProgressChild.jsm",
-    "resource://gre/actors/ZoomChild.jsm",
 
     // Pocket
     "chrome://pocket/content/AboutPocket.jsm",

toolkit/content/widgets/remote-browser.xml

@@ -164,12 +164,12 @@
         <setter><![CDATA[
           let changed = val.toFixed(2) != this._fullZoom.toFixed(2);
 
-          this._fullZoom = val;
-          try {
-            this.messageManager.sendAsyncMessage("FullZoom", {value: val});
-          } catch (ex) {}
-
           if (changed) {
+            this._fullZoom = val;
+            try {
+              this.messageManager.sendAsyncMessage("FullZoom", {value: val});
+            } catch (ex) {}
+
             let event = new Event("FullZoomChange", {bubbles: true});
             this.dispatchEvent(event);
           }
@@ -184,12 +184,12 @@
         <setter><![CDATA[
           let changed = val.toFixed(2) != this._textZoom.toFixed(2);
 
-          this._textZoom = val;
-          try {
-            this.messageManager.sendAsyncMessage("TextZoom", {value: val});
-          } catch (ex) {}
-
           if (changed) {
+            this._textZoom = val;
+            try {
+              this.messageManager.sendAsyncMessage("TextZoom", {value: val});
+            } catch (ex) {}
+
             let event = new Event("TextZoomChange", {bubbles: true});
             this.dispatchEvent(event);
           }