Fix img misalign and hide "by" when nothing selected in new wallpaepr picker ui

chrome/browser/resources/chromeos/wallpaper_manager/css/wallpaper_manager.css

 /* Copyright (c) 2012 The Chromium Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file. */
 
 html {
   height: 100%;
 }
 
 body {
   background-color: #f1f1f1;
@@ skipping 103 matching lines @@
 
 .image-picker [role=listitem] {
   border: 1px solid rgba(0, 0, 0, 0.15);
   border-radius: 4px;
   height: 80px;
   margin: 10px;
   padding: 2px;
   width: 128px;
 }
 
+/* The width and height of img tag need to be set here. Otherwise, incorrect
+ * image size may be used when layout. Some images may be misaligned as a
+ * result. See http://code.google.com/p/chromium/issues/detail?id=148480 for
+ * screen shot.

[flackr, 2012/09/13 02:34:27]

This could potentially show images at the wrong aspect ratio, I assume this is
acceptable for the wallpapers we plan to show for now?

[bshe, 2012/09/13 03:45:48]

Yes. All the thumbnails are downloaded from server and their size are 128x80 for
now.

On 2012/09/13 02:34:27, flackr wrote:

+ */
+.image-picker img {
+  height: 80px;
+  width: 128px;
+}
+
 .image-picker [selected][lead] {
   border: 2px solid rgb(0, 102, 204);
   padding: 1px;
 }
 
-.wallpaper-attr {
+#wallpaper-attr {

[flackr, 2012/09/13 02:34:27]

I don't think there's any need to abbreviate this, can we change it to
wallpaper-attribution, which I assume it's short for.

[bshe, 2012/09/13 03:45:48]

Done.

   -webkit-box-orient: vertical;
   display: -webkit-box;
 }
 
+#wallpaper-attr[hidden] {

[flackr, 2012/09/13 02:34:27]

perhaps just *[hidden]?

[bshe, 2012/09/13 03:45:48]

Done.

+  display: none;
+}
+
 .bottom-bar {
   -webkit-box-align: center;
   -webkit-box-orient: horizontal;
   -webkit-box-pack: end;
   display: -webkit-box;
   height: 30px;
   padding: 10px 15px;
 }
 
 .bottom-bar > .spacer {
   -webkit-box-flex: 1;
 }
 
 /* Custom wallpaper thumbnail container. */
 #preview {
   -webkit-box-shadow: 0 4px 16px rgba(0, 0, 0, 0.2);
   height: 80px;
   width: 128px;
 }