[ios] Set contentsScale before we commit CATransaction

shell/platform/darwin/ios/framework/Source/FlutterOverlayView.h

@@ -23,6 +23,7 @@
 - (instancetype)initWithCoder:(NSCoder*)aDecoder NS_UNAVAILABLE;
 
 - (instancetype)init NS_DESIGNATED_INITIALIZER;
+- (instancetype)initWithContentsScale:(CGFloat)contentsScale;
 - (std::unique_ptr<shell::IOSSurface>)createSoftwareSurface;
 - (std::unique_ptr<shell::IOSSurfaceGL>)createGLSurfaceWithContext:
     (std::shared_ptr<shell::IOSGLContext>)gl_context;

shell/platform/darwin/ios/framework/Source/FlutterOverlayView.mm

@@ -21,13 +21,13 @@
 @implementation FlutterOverlayView
 
 - (instancetype)initWithFrame:(CGRect)frame {
-  @throw([NSException exceptionWithName:@"FlutterOverlayView must initWithDelegate"
+  @throw([NSException exceptionWithName:@"FlutterOverlayView must init or initWithContentsScale"
                                  reason:nil
                                userInfo:nil]);
 }
 
 - (instancetype)initWithCoder:(NSCoder*)aDecoder {
-  @throw([NSException exceptionWithName:@"FlutterOverlayView must initWithDelegate"
+  @throw([NSException exceptionWithName:@"FlutterOverlayView must init or initWithContentsScale"
                                  reason:nil
                                userInfo:nil]);
 }
@@ -43,16 +43,17 @@ - (instancetype)init {
   return self;
 }
 
-- (void)layoutSubviews {
+- (instancetype)initWithContentsScale:(CGFloat)contentsScale {
+  self = [self init];
+
   if ([self.layer isKindOfClass:[CAEAGLLayer class]]) {
     CAEAGLLayer* layer = reinterpret_cast<CAEAGLLayer*>(self.layer);
     layer.allowsGroupOpacity = NO;
-    CGFloat screenScale = [UIScreen mainScreen].scale;
-    layer.contentsScale = screenScale;
-    layer.rasterizationScale = screenScale;
+    layer.contentsScale = contentsScale;
+    layer.rasterizationScale = contentsScale;
   }
 
-  [super layoutSubviews];
+  return self;
 }
 
 + (Class)layerClass {

shell/platform/darwin/ios/framework/Source/FlutterPlatformViews.mm

@@ -243,7 +243,6 @@
     [flutter_view addSubview:overlays_[view_id]->overlay_view.get()];
     active_composition_order_.push_back(view_id);
   }
-
   composition_order_.clear();
   return did_submit;
 }
@@ -277,7 +276,9 @@
     }
     return;
   }
-  FlutterOverlayView* overlay_view = [[FlutterOverlayView alloc] init];
+  auto contentsScale = flutter_view_.get().layer.contentsScale;
+  FlutterOverlayView* overlay_view =
+      [[FlutterOverlayView alloc] initWithContentsScale:contentsScale];
   overlay_view.frame = flutter_view_.get().bounds;
   overlay_view.autoresizingMask =
       (UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight);
@@ -286,6 +287,7 @@
   std::unique_ptr<Surface> surface = ios_surface->CreateSecondaryGPUSurface(gr_context);
   overlays_[overlay_id] = std::make_unique<FlutterPlatformViewLayer>(
       fml::scoped_nsobject<UIView>(overlay_view), std::move(ios_surface), std::move(surface));
+  overlays_gr_context_ = gr_context;
 }
 
 }  // namespace shell