docs(chips): fix typos in comments

Author: n0nick

src/lib/chips/chip-list.ts

@@ -70,7 +70,7 @@ export class MatChipListChange {
 
 
 /**
- * A material design chips component (named ChipList for it's similarity to the List component).
+ * A material design chips component (named ChipList for its similarity to the List component).
  */
 @Component({
   moduleId: module.id,

src/lib/chips/chip.ts

@@ -180,8 +180,8 @@ export class MatChip extends _MatChipMixinBase implements FocusableOption, OnDes
 
   /**
    * Whether or not the chip is selectable. When a chip is not selectable,
-   * changes to it's selected state are always ignored. By default a chip is
-   * selectable, and it becomes non-selectable if it's parent chip list is
+   * changes to its selected state are always ignored. By default a chip is
+   * selectable, and it becomes non-selectable if its parent chip list is
    * not selectable.
    */
   @Input()