[minor] tools/skottie_ios_app/Skia*Context: remember to cast

This will make a client builder happy.

Change-Id: Ia7b79768dc7ba9806d854740d1f7c4b2c02fa845
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/264417
Commit-Queue: Hal Canary <halcanary@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: Hal Canary <halcanary@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>

tools/skottie_ios_app/SkiaGLContext.mm

@@ -139,7 +139,7 @@ static sk_sp<SkSurface> make_gl_surface(GrContext* grContext, int width, int hei
     return skiaView;
 }
 - (SkiaViewController*) getViewController:(UIView*)view {
-    return [view isKindOfClass:[SkiaGLView class]] ? [view controller] : nil;
+    return [view isKindOfClass:[SkiaGLView class]] ? [(SkiaGLView*)view controller] : nil;
 }
 @end
 

tools/skottie_ios_app/SkiaMetalContext.mm

@@ -110,7 +110,7 @@
 }
 
 - (SkiaViewController*) getViewController:(UIView*)view {
-    return [view isKindOfClass:[SkiaMtkView class]] ? [view controller] : nil;
+    return [view isKindOfClass:[SkiaMtkView class]] ? [(SkiaMtkView*)view controller] : nil;
 }
 @end
 

tools/skottie_ios_app/SkiaUIContext.mm

@@ -59,7 +59,7 @@
     return skiaView;
 }
 - (SkiaViewController*) getViewController:(UIView*)view {
-    return [view isKindOfClass:[SkiaUIView class]] ? [view controller] : nil;
+    return [view isKindOfClass:[SkiaUIView class]] ? [(SkiaUIView*)view controller] : nil;
 }
 @end