Bug 345178 Remove tooltip width limit for tab-preview tooltips and improve preview behavior for small images

r+sr=neil

themes/classic/navigator/mac/tabbrowser.css

@@ -65,3 +65,7 @@ tab[busy] {
     position: relative;
     list-style-image: url('chrome://global/skin/icons/tab-drag-indicator.gif');
 }
+
+tooltip[tabpreview="true"] {
+  max-width: none;
+}

themes/classic/navigator/win/tabbrowser.css

@@ -65,3 +65,7 @@ tab[busy] {
     position: relative;
     list-style-image: url('chrome://global/skin/icons/tab-drag-indicator.gif');
 }
+
+tooltip[tabpreview="true"] {
+  max-width: none;
+}