Bug 1217129: Part 4a - Allow creating CustomizableUI widgets without tooltips. r=gijs

--HG--
extra : commitid : 4J9bvN6e3P6
extra : rebase_source : d9209f219d747b2a9e22078a630af8b423e08776
extra : source : 71f46fe62f59385d6a39d426fd571ed08e46a403

browser/components/customizableui/CustomizableUI.jsm

@@ -1342,7 +1342,9 @@ var CustomizableUIInternal = {
       }
 
       let tooltip = this.getLocalizedProperty(aWidget, "tooltiptext", additionalTooltipArguments);
-      node.setAttribute("tooltiptext", tooltip);
+      if (tooltip) {
+        node.setAttribute("tooltiptext", tooltip);
+      }
       node.setAttribute("class", "toolbarbutton-1 chromeclass-toolbar-additional");
 
       let commandHandler = this.handleWidgetCommand.bind(this, aWidget, node);
@@ -1385,6 +1387,8 @@ var CustomizableUIInternal = {
   },
 
   getLocalizedProperty: function(aWidget, aProp, aFormatArgs, aDef) {
+    const kReqStringProps = ["label"];
+
     if (typeof aWidget == "string") {
       aWidget = gPalette.get(aWidget);
     }
@@ -1395,7 +1399,7 @@ var CustomizableUIInternal = {
     // Let widgets pass their own string identifiers or strings, so that
     // we can use strings which aren't the default (in case string ids change)
     // and so that non-builtin-widgets can also provide labels, tooltips, etc.
-    if (aWidget[aProp]) {
+    if (aWidget[aProp] != null) {
       name = aWidget[aProp];
       // By using this as the default, if a widget provides a full string rather
       // than a string ID for localization, we will fall back to that string
@@ -1412,7 +1416,9 @@ var CustomizableUIInternal = {
       }
       return gWidgetsBundle.GetStringFromName(name) || def;
     } catch(ex) {
-      if (!def) {
+      // If an empty string was explicitly passed, treat it as an actual
+      // value rather than a missing property.
+      if (!def && (name != "" || kReqStringProps.includes(aProp))) {
         ERROR("Could not localize property '" + name + "'.");
       }
     }