Respond to CR.

// FREEBIE

Signal/src/ViewControllers/ProfileViewController.m

@@ -346,11 +346,12 @@ NSString *const kProfileView_LastPresentedDate = @"kProfileView_LastPresentedDat
     // The save button is only used in "registration" and "upgrade or nag" modes.
     if (self.hasUnsavedChanges) {
         self.saveButton.enabled = YES;
-        [self.saveButton setBackgroundColors:[UIColor ows_signalBrandBlueColor]];
+        [self.saveButton setBackgroundColorsWithUpColor:[UIColor ows_signalBrandBlueColor]];
     } else {
         self.saveButton.enabled = NO;
         [self.saveButton
-            setBackgroundColors:[[UIColor ows_signalBrandBlueColor] blendWithColor:[UIColor whiteColor] alpha:0.5f]];
+            setBackgroundColorsWithUpColor:[[UIColor ows_signalBrandBlueColor] blendWithColor:[UIColor whiteColor]
+                                                                                        alpha:0.5f]];
     }
 }
 

Signal/src/ViewControllers/SelectRecipientViewController.m

@@ -379,7 +379,7 @@ NSString *const kSelectRecipientViewControllerCellIdentifier = @"kSelectRecipien
     BOOL isEnabled = [self hasValidPhoneNumber];
     self.phoneNumberButton.enabled = isEnabled;
     [self.phoneNumberButton
-        setBackgroundColors:(isEnabled ? [UIColor ows_signalBrandBlueColor] : [UIColor lightGrayColor])];
+        setBackgroundColorsWithUpColor:(isEnabled ? [UIColor ows_signalBrandBlueColor] : [UIColor lightGrayColor])];
 }
 
 #pragma mark - CountryCodeViewControllerDelegate

Signal/src/util/UIImage+OWS.m

@@ -170,6 +170,7 @@
 
 + (UIImage *)imageWithColor:(UIColor *)color
 {
+    OWSAssert([NSThread isMainThread]);
     OWSAssert(color);
 
     return [self imageWithColor:color size:CGSizeMake(1.f, 1.f)];
@@ -177,6 +178,7 @@
 
 + (UIImage *)imageWithColor:(UIColor *)color size:(CGSize)size
 {
+    OWSAssert([NSThread isMainThread]);
     OWSAssert(color);
 
     CGRect rect = CGRectMake(0.0f, 0.0f, size.width, size.height);

Signal/src/views/OWSFlatButton.swift

@@ -7,16 +7,24 @@ import Foundation
 @objc class OWSFlatButton: UIView {
     let TAG = "[OWSFlatButton]"
 
-    private var button: UIButton?
+    private let button: UIButton
 
     private var pressedBlock : (() -> Void)?
 
     private var upColor: UIColor?
     private var downColor: UIColor?
 
+    override var backgroundColor: UIColor? {
+        willSet {
+            owsFail("Use setBackgroundColors(upColor:) instead.")
+        }
+    }
+
     init() {
         AssertIsOnMainThread()
 
+        button = UIButton(type:.custom)
+
         super.init(frame:CGRect.zero)
 
         createContent()
@@ -24,13 +32,14 @@ import Foundation
 
     @available(*, unavailable, message:"use default constructor instead.")
     required init?(coder aDecoder: NSCoder) {
+        button = UIButton(type:.custom)
+
         super.init(coder: aDecoder)
+
         owsFail("\(self.TAG) invalid constructor")
     }
 
     private func createContent() {
-        let button = UIButton(type:.custom)
-        self.button = button
         self.addSubview(button)
         button.addTarget(self, action:#selector(buttonPressed), for:.touchUpInside)
         button.autoPinWidthToSuperview()
@@ -49,7 +58,7 @@ import Foundation
         button.setTitle(title:title,
                         font: font,
                         titleColor: titleColor )
-        button.setBackgroundColors(backgroundColor)
+        button.setBackgroundColors(upColor:backgroundColor)
         button.useDefaultCornerRadius()
         button.setSize(width:width, height:height)
         button.addTarget(target:target, selector:selector)
@@ -83,7 +92,7 @@ import Foundation
         button.setTitle(title:title,
                         font: font,
                         titleColor: titleColor )
-        button.setBackgroundColors(backgroundColor)
+        button.setBackgroundColors(upColor:backgroundColor)
         button.useDefaultCornerRadius()
         button.addTarget(target:target, selector:selector)
         return button
@@ -98,10 +107,6 @@ import Foundation
 
     public func setTitle(title: String, font: UIFont,
                          titleColor: UIColor ) {
-        guard let button = self.button else {
-            owsFail("Missing button")
-            return
-        }
         button.setTitle(title, for: .normal)
         button.setTitleColor(titleColor, for: .normal)
         button.titleLabel!.font = font
@@ -109,33 +114,21 @@ import Foundation
 
     public func setBackgroundColors(upColor: UIColor,
                                     downColor: UIColor ) {
-        guard let button = self.button else {
-            owsFail("Missing button")
-            return
-        }
         button.setBackgroundImage(UIImage(color:upColor), for: .normal)
         button.setBackgroundImage(UIImage(color:downColor), for: .highlighted)
     }
 
-    public func setBackgroundColors(_ backgroundColor: UIColor ) {
+    public func setBackgroundColors(upColor: UIColor ) {
-        setBackgroundColors(upColor: backgroundColor,
+        setBackgroundColors(upColor: upColor,
-                            downColor: backgroundColor.withAlphaComponent(0.7) )
+                            downColor: upColor.withAlphaComponent(0.7) )
     }
 
     public func setSize(width: CGFloat, height: CGFloat) {
-        guard let button = self.button else {
-            owsFail("Missing button")
-            return
-        }
         button.autoSetDimension(.width, toSize:width)
         button.autoSetDimension(.height, toSize:height)
     }
 
     public func useDefaultCornerRadius() {
-        guard let button = self.button else {
-            owsFail("Missing button")
-            return
-        }
         // To my eye, this radius tends to look right regardless of button size
         // (within reason) or device size. 
         button.layer.cornerRadius = 5
@@ -143,19 +136,11 @@ import Foundation
     }
 
     public func setEnabled(_ isEnabled: Bool) {
-        guard let button = self.button else {
-            owsFail("Missing button")
-            return
-        }
         button.isEnabled = isEnabled
     }
 
     public func addTarget(target:Any,
                           selector: Selector) {
-        guard let button = self.button else {
-            owsFail("Missing button")
-            return
-        }
         button.addTarget(target, action:selector, for:.touchUpInside)
     }
 
@@ -168,9 +153,6 @@ import Foundation
     }
 
     internal func buttonPressed() {
-        guard let pressedBlock = pressedBlock else {
+        pressedBlock?()
-            return
-        }
-        pressedBlock()
     }
 }