fix(select):update implementation of disable offset

Author: timmoy

src/lib/select/select.ts

@@ -1114,45 +1114,43 @@ export class MatSelect extends _MatSelectMixinBase implements AfterContentInit,
    */
   private _calculateOverlayOffsetY(selectedIndex: number, scrollBuffer: number,
                                   maxScroll: number): number {
-    // Only enable offset for larger lists
-	if (this._getItemCount() > 10) { 	  
-	  const itemHeight = this._getItemHeight();
-      const optionHeightAdjustment = (itemHeight - this._triggerRect.height) / 2;
-      const maxOptionsDisplayed = Math.floor(SELECT_PANEL_MAX_HEIGHT / itemHeight);
-      let optionOffsetFromPanelTop: number;
-
-      if (this._scrollTop === 0) {
-        optionOffsetFromPanelTop = selectedIndex * itemHeight;
-      } else if (this._scrollTop === maxScroll) {
-        const firstDisplayedIndex = this._getItemCount() - maxOptionsDisplayed;
-        const selectedDisplayIndex = selectedIndex - firstDisplayedIndex;
-
-        // The first item is partially out of the viewport. Therefore we need to calculate what
-        // portion of it is shown in the viewport and account for it in our offset.
-        let partialItemHeight =
-            itemHeight - (this._getItemCount() * itemHeight - SELECT_PANEL_MAX_HEIGHT) % itemHeight;
-
-        // Because the panel height is longer than the height of the options alone,
-        // there is always extra padding at the top or bottom of the panel. When
-        // scrolled to the very bottom, this padding is at the top of the panel and
-        // must be added to the offset.
-        optionOffsetFromPanelTop = selectedDisplayIndex * itemHeight + partialItemHeight;
-      } else {
-        // If the option was scrolled to the middle of the panel using a scroll buffer,
-        // its offset will be the scroll buffer minus the half height that was added to
-        // center it.
-        optionOffsetFromPanelTop = scrollBuffer - itemHeight / 2;
-      }
+    const itemHeight = this._getItemHeight();
+    const optionHeightAdjustment = (itemHeight - this._triggerRect.height) / 2;
+    const maxOptionsDisplayed = Math.floor(SELECT_PANEL_MAX_HEIGHT / itemHeight);
+    let optionOffsetFromPanelTop: number;
+
+    // Disable offset for smaller lists by returning 0 as value to offset
+    if (this._getItemCount() <= maxOptionsDisplayed) {
+      return 0;
+    }
+
+    if (this._scrollTop === 0) {
+      optionOffsetFromPanelTop = selectedIndex * itemHeight;
+    } else if (this._scrollTop === maxScroll) {
+      const firstDisplayedIndex = this._getItemCount() - maxOptionsDisplayed;
+      const selectedDisplayIndex = selectedIndex - firstDisplayedIndex;
+
+      // The first item is partially out of the viewport. Therefore we need to calculate what
+      // portion of it is shown in the viewport and account for it in our offset.
+      let partialItemHeight =
+          itemHeight - (this._getItemCount() * itemHeight - SELECT_PANEL_MAX_HEIGHT) % itemHeight;
+
+      // Because the panel height is longer than the height of the options alone,
+      // there is always extra padding at the top or bottom of the panel. When
+      // scrolled to the very bottom, this padding is at the top of the panel and
+      // must be added to the offset.
+      optionOffsetFromPanelTop = selectedDisplayIndex * itemHeight + partialItemHeight;
+    } else {
+      // If the option was scrolled to the middle of the panel using a scroll buffer,
+      // its offset will be the scroll buffer minus the half height that was added to
+      // center it.
+      optionOffsetFromPanelTop = scrollBuffer - itemHeight / 2;
+    }
 
-      // The final offset is the option's offset from the top, adjusted for the height
-      // difference, multiplied by -1 to ensure that the overlay moves in the correct
-      // direction up the page.
-	
-	  return optionOffsetFromPanelTop * -1 - optionHeightAdjustment;
-	} else {  
-	  // disable offset for smaller lists
-	  return 0;
-	}
+    // The final offset is the option's offset from the top, adjusted for the height
+    // difference, multiplied by -1 to ensure that the overlay moves in the correct
+    // direction up the page.
+    return optionOffsetFromPanelTop * -1 - optionHeightAdjustment;
   }
 
   /**