Add a half slew of generic command execution/completion/code coverage tests. Add unhandled exception checking to tests. Fix some detected merge artifacts.

common/modules/addons.jsm

@@ -302,7 +302,7 @@ var AddonList = Class("AddonList", {
         if (addon && addon.id in this.addons)
             this.addons[addon.id].update();
         if (this.ready)
-            this.modules.mow.resize(false);
+            this.modules.commandline.updateOutputHeight(false);
     },
 
     onDisabled:           function (addon) { this.update(addon); },

common/modules/base.jsm

@@ -658,7 +658,7 @@ function Class() {
 
     var Constructor = eval(String.replace(<![CDATA[
         (function constructor() {
-            let self = Object.create(Constructor.prototype, {
+            var self = Object.create(Constructor.prototype, {
                 constructor: { value: Constructor },
             });
             self.instance = self;

common/modules/completion.jsm

@@ -870,10 +870,15 @@ var Completion = Module("completion", {
             context = context.contexts["/list"];
             context.wait();
 
+            let contexts = context.contextList.filter(function (c) c.hasItems && c.items.length);
+            if (!contexts.length)
+                contexts = context.contextList.filter(function (c) c.hasItems).slice(0, 1);
+            if (!contexts.length)
+                contexts = context.contextList.slice(-1);
+
             modules.commandline.commandOutput(
                 <div highlight="Completions">
-                    { template.map(context.contextList.filter(function (c) c.hasItems && c.items.length),
-                        function (context)
+                    { template.map(contexts, function (context)
                             template.completionRow(context.title, "CompTitle") +
                             template.map(context.items, function (item) context.createRow(item), null, 100)) }
                 </div>);

common/modules/downloads.jsm

@@ -296,7 +296,7 @@ var DownloadList = Class("DownloadList",
             else {
                 this.addDownload(download.id);
 
-                this.modules.mow.resize(false);
+                this.modules.commandline.updateOutputHeight(false);
                 this.nodes.list.scrollIntoView(false);
             }
             this.update();

common/modules/util.jsm

@@ -1344,13 +1344,16 @@ var Util = Module("Util", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReference]),
         });
     },
 
-    maxErrors: 15,
+    errorCount: 0,
     errors: Class.memoize(function () []),
+    maxErrors: 15,
     reportError: function (error) {
         if (Cu.reportError)
             Cu.reportError(error);
 
         try {
+            this.errorCount++;
+
             let obj = update({}, error, {
                 toString: function () String(error),
                 stack: <>{util.stackLines(String(error.stack || Error().stack)).join("\n").replace(/^/mg, "\t")}</>