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

r+sr=neil

themes/classic/global/mac/browser.css

@@ -54,3 +54,7 @@ tab[busy] {
   margin: 0px;
   list-style-image: url("chrome://global/skin/icons/tab-new.gif");
 }
+
+tooltip[tabpreview="true"] {
+  max-width: none;
+}

themes/classic/global/win/browser.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;
+}

xpfe/global/resources/content/bindings/tabbrowser.xml

@@ -214,6 +214,7 @@
 
           if (!this.mPrefs.getBoolPref("browser.tabs.tooltippreview.enable")) {
             label.removeAttribute("width");
+            aPopup.removeAttribute("tabpreview");
             return true;
           }
 
@@ -225,6 +226,7 @@
           }
 
           label.width = 0;
+          aPopup.setAttribute("tabpreview", "true");
           var win = b.contentWindow;
           var w = win.innerWidth;
           var h = win.innerHeight;
@@ -243,7 +245,10 @@
             ctx.fillRect(0, 0, canvasW, canvasH);
             var img = b.contentDocument.body.firstChild;
             var ratio = img.naturalHeight / img.naturalWidth;
-            if (ratio * canvasW > canvasH) {
+            if (img.naturalHeight <= canvasH && img.naturalWidth <= canvasW) {
+              ctx.drawImage(img, 0, 0, img.naturalWidth, img.naturalHeight);
+            }
+            else if (ratio * canvasW > canvasH) {
               ctx.drawImage(img, 0, 0, canvasH / ratio, canvasH);
             }
             else {