chore(select): fix flaky positioning test (angular#12496)

Fixes a flaky test that is failing on iOS.

Author: crisbeto

src/lib/button/button.ts

@@ -33,9 +33,6 @@ import {ANIMATION_MODULE_TYPE} from '@angular/platform-browser/animations';
 /** Default color palette for round buttons (mat-fab and mat-mini-fab) */
 const DEFAULT_ROUND_BUTTON_COLOR = 'accent';
 
-/** Default color palette for flat buttons (mat-flat-button) */
-const DEFAULT_FLAT_BUTTON_COLOR = 'primary';
-
 /**
  * List of classes to add to MatButton instances based on host attributes to
  * style as different variants.
@@ -113,8 +110,6 @@ export class MatButton extends _MatButtonMixinBase
 
     if (this.isRoundButton) {
       this.color = DEFAULT_ROUND_BUTTON_COLOR;
-    } else if (this._hasHostAttributes('mat-flat-button')) {
-      this.color = DEFAULT_FLAT_BUTTON_COLOR;
     }
   }
 

src/lib/select/select.spec.ts

@@ -3318,7 +3318,8 @@ describe('MatSelect', () => {
 
         let panelLeft = document.querySelector('.mat-select-panel')!.getBoundingClientRect().left;
 
-        expect(panelLeft).toBeGreaterThan(0, `Expected select panel to be inside the viewport.`);
+        expect(panelLeft)
+            .toBeGreaterThanOrEqual(0, `Expected select panel to be inside the viewport.`);
 
         fixture.componentInstance.select.close();
         fixture.detectChanges();
@@ -3330,7 +3331,7 @@ describe('MatSelect', () => {
 
         panelLeft = document.querySelector('.mat-select-panel')!.getBoundingClientRect().left;
 
-        expect(panelLeft).toBeGreaterThan(0,
+        expect(panelLeft).toBeGreaterThanOrEqual(0,
             `Expected select panel continue being inside the viewport.`);
       }));
     });