cleanup(select): remove runtime checkbox padding calculation workaround (#16827)

(cherry picked from commit b0495f6)

Author: josephperrott

src/material/select/select.ts

@@ -119,11 +119,11 @@ export const SELECT_ITEM_HEIGHT_EM = 3;
  * multi-selection mode.
  *
  * Calculated as:
- * (SELECT_PANEL_PADDING_X * 1.5) + 20 = 44
+ * (SELECT_PANEL_PADDING_X * 1.5) + 16 = 40
  * The padding is multiplied by 1.5 because the checkbox's margin is half the padding.
  * The checkbox width is 16px.
  */
-export let SELECT_MULTIPLE_PANEL_PADDING_X = 0;
+export const SELECT_MULTIPLE_PANEL_PADDING_X = SELECT_PANEL_PADDING_X * 1.5 + 16;
 
 /**
  * The select panel will only "fit" inside the viewport if it is positioned at
@@ -805,7 +805,6 @@ export class MatSelect extends _MatSelectMixinBase implements AfterContentInit,
    */
   _onAttached(): void {
     this.overlayDir.positionChange.pipe(take(1)).subscribe(() => {
-      this._setPseudoCheckboxPaddingSize();
       this._changeDetectorRef.detectChanges();
       this._calculateOverlayOffsetX();
       this.panel.nativeElement.scrollTop = this._scrollTop;
@@ -817,17 +816,6 @@ export class MatSelect extends _MatSelectMixinBase implements AfterContentInit,
     return this._parentFormField ? `mat-${this._parentFormField.color}` : '';
   }
 
-  // TODO(josephperrott): Remove after 2018 spec updates are fully merged.
-  /** Sets the pseudo checkbox padding size based on the width of the pseudo checkbox. */
-  private _setPseudoCheckboxPaddingSize() {
-    if (!SELECT_MULTIPLE_PANEL_PADDING_X && this.multiple) {
-      const pseudoCheckbox = this.panel.nativeElement.querySelector('.mat-pseudo-checkbox');
-      if (pseudoCheckbox) {
-        SELECT_MULTIPLE_PANEL_PADDING_X = SELECT_PANEL_PADDING_X * 1.5 + pseudoCheckbox.offsetWidth;
-      }
-    }
-  }
-
   /** Whether the select has a value. */
   get empty(): boolean {
     return !this._selectionModel || this._selectionModel.isEmpty();

tools/public_api_guard/material/select.d.ts

@@ -114,7 +114,7 @@ export declare class MatSelectTrigger {
 
 export declare const SELECT_ITEM_HEIGHT_EM = 3;
 
-export declare let SELECT_MULTIPLE_PANEL_PADDING_X: number;
+export declare const SELECT_MULTIPLE_PANEL_PADDING_X: number;
 
 export declare const SELECT_PANEL_INDENT_PADDING_X: number;