fixes #8702 until Normalize.css starts handling this

dist/css/bootstrap.css

@@ -316,6 +316,13 @@ textarea {
   line-height: inherit;
 }
 
+button,
+input,
+select[multiple],
+textarea {
+  background-image: none;
+}
+
 a {
   color: #428bca;
   text-decoration: none;

less/scaffolding.less

@@ -39,6 +39,14 @@ textarea {
   line-height: inherit;
 }
 
+// Reset unusual Firefox-on-Android default style, see https://github.com/necolas/normalize.css/issues/214
+button,
+input,
+select[multiple],
+textarea {
+  background-image: none;
+}
+
 
 // Links
 // -------------------------