fix(material/icon/testing): Adds size specs to fake icon (#18306)

Adds size specs to the fake icon to match specs of the real implementation.
Without this, the rendered blank icon has the default size of an SVG element
which is 300x150px which can break layouts.

Author: osuritz

src/material/icon/testing/fake-icon-registry.ts

@@ -83,6 +83,12 @@ export class FakeMatIconRegistry implements PublicApi<MatIconRegistry>, OnDestro
   private _generateEmptySvg(): SVGElement {
     const emptySvg = document.createElementNS('http://www.w3.org/2000/svg', 'svg');
     emptySvg.classList.add('fake-testing-svg');
+    // Emulate real icon characteristics from `MatIconRegistry` so size remains consistent in tests.
+    emptySvg.setAttribute('fit', '');
+    emptySvg.setAttribute('height', '100%');
+    emptySvg.setAttribute('width', '100%');
+    emptySvg.setAttribute('preserveAspectRatio', 'xMidYMid meet');
+    emptySvg.setAttribute('focusable', 'false');
     return emptySvg;
   }
 }