Fix iOS builds after ShellView refactor on Android

sky/shell/ios/platform_view_ios.mm

Index: sky/shell/ios/platform_view_ios.mm
diff --git a/sky/shell/ios/platform_view_ios.mm b/sky/shell/ios/platform_view_ios.mm
index 492527733cc1554f70ae1de7f7288467e2ecd179..3c5f90d16077221a5ad5d0ca0e1205d01864efc2 100644
--- a/sky/shell/ios/platform_view_ios.mm
+++ b/sky/shell/ios/platform_view_ios.mm
@@ -11,6 +11,13 @@ PlatformView* PlatformView::Create(const Config& config) {
   return new PlatformViewIOS(config);
 }
 
+PlatformViewIOS::PlatformViewIOS(const Config& config)
+  : PlatformView(config) {
+}
+
+PlatformViewIOS::~PlatformViewIOS() {
+}
+
 void PlatformViewIOS::SurfaceCreated(gfx::AcceleratedWidget widget) {
   DCHECK(window_ == 0);
   window_ = widget;