Bug 1081296 - Add sumo link for promotional translation doorhanger. r=florian

browser/components/translation/translation-infobar.xml

@@ -31,7 +31,8 @@
                                anonid="welcomeHeadline"/>
               <xul:description class="translation-welcome-body" anonid="welcomeBody"/>
               <xul:hbox align="center">
-                <xul:label anonid="learnMore" class="plain text-link"/>
+                <xul:label anonid="learnMore" class="plain text-link"
+                           onclick="openUILinkIn('https://support.mozilla.org/en-US/products/firefox/automatic-translation', 'tab'); this.parentNode.parentNode.parentNode.hidePopup();"/>
                 <xul:spacer flex="1"/>
                 <xul:button class="translate-infobar-element" anonid="thanksButton"
                             onclick="this.parentNode.parentNode.parentNode.hidePopup();"/>
@@ -215,7 +216,8 @@
               this.state = aTranslation.state;
 
             const kWelcomePref = "browser.translation.ui.welcomeMessageShown";
-            if (Services.prefs.prefHasUserValue(kWelcomePref))
+            if (Services.prefs.prefHasUserValue(kWelcomePref) ||
+                this.translation.browser != gBrowser.selectedBrowser)
               return;
 
             this.addEventListener("transitionend", function onShown() {