Fix ActivityIndicator layout issues (#991)

* Increase the default content hugging priority for ActivityIndicator

* Disable implicit animations during content layer layout

* Remove unnecesary content hugging priority override

Stripe/LinkEmailElement.swift

@@ -17,7 +17,6 @@ class LinkEmailElement: Element {
     private let activityIndicator: ActivityIndicator = {
         // TODO: Consider adding the activity indicator to TextFieldView
         let activityIndicator = ActivityIndicator(size: .medium)
-        activityIndicator.setContentHuggingPriority(.required, for: .horizontal)
         activityIndicator.setContentCompressionResistancePriority(.required, for: .horizontal)
         return activityIndicator
     }()
@@ -89,6 +88,4 @@ extension LinkEmailElement: ElementDelegate {
     func continueToNextField(element: Element) {
         delegate?.continueToNextField(element: self)
     }
-
-
 }

StripeUICore/StripeUICore/Source/Controls/ActivityIndicator.swift

@@ -113,6 +113,9 @@ import UIKit
         super.init(frame: .zero)
         layer.addSublayer(contentLayer)
 
+        setContentHuggingPriority(.defaultHigh, for: .horizontal)
+        setContentHuggingPriority(.defaultHigh, for: .vertical)
+
         updateVisibility()
         updatecolor()
 
@@ -144,8 +147,16 @@ import UIKit
 
     public override func layoutSubviews() {
         super.layoutSubviews()
+
+        CATransaction.begin()
+        // `bounds` and `position` are both animatable. Disable actions to turn off
+        // implicit animations when updating them.
+        CATransaction.setDisableActions(true)
+
         contentLayer.bounds = CGRect(origin: .zero, size: intrinsicContentSize)
         contentLayer.position = CGPoint(x: bounds.midX, y: bounds.midY)
+
+        CATransaction.commit()
     }
 
     public override func willMove(toWindow newWindow: UIWindow?) {