fix(select,input): inconsistent disabled text color

Fixes the select and input having different disabled text colors and not taking colors from the palettes.

Fixes angular#7793.

src/lib/input/_input-theme.scss

@@ -6,10 +6,9 @@
 
 @mixin mat-input-theme($theme) {
   $foreground: map-get($theme, foreground);
-  $is-dark-theme: map-get($theme, is-dark);
 
   .mat-input-element:disabled {
-    color: mat-color($foreground, secondary-text, if($is-dark-theme, 0.7, 0.42));
+    color: mat-color($foreground, disabled-text);
   }
 }
 

src/lib/select/_select-theme.scss

@@ -10,12 +10,6 @@
   $primary: map-get($theme, primary);
   $accent: map-get($theme, accent);
   $warn: map-get($theme, warn);
-  $is-dark-theme: map-get($theme, is-dark);
-
-  .mat-select-disabled .mat-select-value,
-  .mat-select-arrow {
-    color: mat-color($foreground, secondary-text);
-  }
 
   .mat-select-content, .mat-select-panel-done-animating {
     background: mat-color($background, card);
@@ -25,6 +19,14 @@
     color: mat-color($foreground, text);
   }
 
+  .mat-select-disabled .mat-select-value {
+    color: mat-color($foreground, disabled-text);
+  }
+
+  .mat-select-arrow {
+    color: mat-color($foreground, secondary-text);
+  }
+
   .mat-select-panel {
     .mat-option.mat-selected:not(.mat-option-multiple) {
       background: mat-color($background, hover, 0.12);
@@ -51,13 +53,9 @@
     }
 
     .mat-select.mat-select-disabled .mat-select-arrow {
-      color: mat-color($foreground, secondary-text);
+      color: mat-color($foreground, disabled-text);
     }
   }
-
-  .mat-select.mat-select-disabled .mat-select-arrow {
-    color: mat-color($warn);
-  }
 }
 
 @mixin mat-select-typography($config) {