add color getter to ComparableColorDrawable

Summary: ComparableColorDrawable didn't have a way to read it's color. This diff adds a getter method `getColor` to it.

Reviewed By: muraziz

Differential Revision: D15469092

fbshipit-source-id: fb8ab03688e2ea3e4cd073437a8817b29fcd0416

litho-core/src/main/java/com/facebook/litho/drawable/ComparableColorDrawable.java

@@ -40,6 +40,10 @@ public boolean isEquivalentTo(ComparableDrawable other) {
     return mColor == ((ComparableColorDrawable) other).mColor;
   }
 
+  public @ColorInt int getColor() {
+    return mColor;
+  }
+
   public static ComparableColorDrawable create(@ColorInt int color) {
     return new ComparableColorDrawable(color);
   }