Bug 1124479 - Remove unused plus-button styles from aboutReader.css. r=margaret

mobile/android/themes/core/aboutReader.css

@@ -509,14 +509,6 @@ body {
     background-image: url('chrome://browser/skin/images/reader-dropdown-arrow-hdpi.png');
   }
 
-  .step-control > .plus-button {
-    background-image: url('chrome://browser/skin/images/reader-plus-icon-hdpi.png');
-  }
-
-  .step-control > .minus-button {
-    background-image: url('chrome://browser/skin/images/reader-minus-icon-hdpi.png');
-  }
-
   .toggle-button.on {
     background-image: url('chrome://browser/skin/images/reader-toggle-on-icon-hdpi.png');
   }
@@ -539,14 +531,6 @@ body {
     background-image: url('chrome://browser/skin/images/reader-dropdown-arrow-xhdpi.png');
   }
 
-  .step-control > .plus-button {
-    background-image: url('chrome://browser/skin/images/reader-plus-icon-xhdpi.png');
-  }
-
-  .step-control > .minus-button {
-    background-image: url('chrome://browser/skin/images/reader-minus-icon-xhdpi.png');
-  }
-
   .toggle-button.on {
     background-image: url('chrome://browser/skin/images/reader-toggle-on-icon-xhdpi.png');
   }

mobile/android/themes/core/jar.mn

@@ -85,12 +85,7 @@ chrome.jar:
   skin/images/about-btn-darkgrey.png        (images/about-btn-darkgrey.png)
   skin/images/logo-hdpi.png                 (images/logo-hdpi.png)
   skin/images/wordmark-hdpi.png             (images/wordmark-hdpi.png)
-  skin/images/reader-plus-icon-mdpi.png     (images/reader-plus-icon-mdpi.png)
-  skin/images/reader-plus-icon-hdpi.png     (images/reader-plus-icon-hdpi.png)
   skin/images/reader-plus-icon-xhdpi.png    (images/reader-plus-icon-xhdpi.png)
-  skin/images/reader-minus-icon-mdpi.png    (images/reader-minus-icon-mdpi.png)
-  skin/images/reader-minus-icon-hdpi.png    (images/reader-minus-icon-hdpi.png)
-  skin/images/reader-minus-icon-xhdpi.png   (images/reader-minus-icon-xhdpi.png)
   skin/images/reader-dropdown-arrow-mdpi.png     (images/reader-dropdown-arrow-mdpi.png)
   skin/images/reader-dropdown-arrow-hdpi.png     (images/reader-dropdown-arrow-hdpi.png)
   skin/images/reader-dropdown-arrow-xhdpi.png    (images/reader-dropdown-arrow-xhdpi.png)