Added mixin to be applied on input:disabled

Author: robertop87

paper-input-container.html

@@ -99,6 +99,7 @@
 `--paper-input-container-label-focus` | Mixin applied to the label when the input is focused | `{}`
 `--paper-input-container-label-floating` | Mixin applied to the label when floating | `{}`
 `--paper-input-container-input` | Mixin applied to the input | `{}`
+`--paper-input-container-input-disabled` | Mixin applied to the input when the component is disabled | `{}`
 `--paper-input-container-input-focus` | Mixin applied to the input when focused | `{}`
 `--paper-input-container-input-invalid` | Mixin applied to the input when invalid | `{}`
 `--paper-input-container-input-webkit-spinner` | Mixin applied to the webkit spinner | `{}`

paper-input.html

@@ -102,6 +102,10 @@
         @apply --paper-input-container-input;
       }
 
+      input:disabled {
+        @apply --paper-input-container-input-disabled;
+      }
+
       input::-webkit-outer-spin-button,
       input::-webkit-inner-spin-button {
         @apply --paper-input-container-input-webkit-spinner;