[Button] Fix the issue that button state is not updated

On Lollipop, when first assigned as View's background, RippleDrawable won't/can't propagate states to its content drawable. This causes the issue that the state relevant features like stroke colors are not correctly updated when the background is recreated. Explicitly assigns states to the content drawable to fix the issue.

Resolves #1422

PiperOrigin-RevId: 442676637

lib/java/com/google/android/material/button/MaterialButtonHelper.java

@@ -143,6 +143,11 @@ private void updateBackground() {
     MaterialShapeDrawable materialShapeDrawable = getMaterialShapeDrawable();
     if (materialShapeDrawable != null) {
       materialShapeDrawable.setElevation(elevation);
+      if (IS_LOLLIPOP) {
+        // Fix the issue that on Lollipop, when first assigned as View's background, RippleDrawable
+        // won't/can't propagate states to its content drawable. (It somehow works afterwards.)
+        materialShapeDrawable.setState(materialButton.getDrawableState());
+      }
     }
   }