[Impeller] Don't override user specification on Vulkan validation in …

…unopt.

This overrides the documented behavior silently but only in unopt. Make
opt and unopt modes behave the same. Disabling validation is frequently
necessary to test behavior on simulators or when connecting to
Renderdoc.

impeller/renderer/backend/vulkan/context_vk.cc

@@ -157,18 +157,8 @@ void ContextVK::Setup(Settings settings) {
   auto& dispatcher = VULKAN_HPP_DEFAULT_DISPATCHER;
   dispatcher.init(settings.proc_address_callback);
 
-  // Enable Vulkan validation if either:
-  // 1. The user has explicitly enabled it.
-  // 2. We are in a combination of debug mode, and running on Android.
-  // (It's possible 2 is overly conservative and we can simplify this)
-  auto enable_validation = settings.enable_validation;
-
-#if defined(FML_OS_ANDROID) && !defined(NDEBUG)
-  enable_validation = true;
-#endif
-
   auto caps = std::shared_ptr<CapabilitiesVK>(new CapabilitiesVK(
-      enable_validation, settings.fatal_missing_validations));
+      settings.enable_validation, settings.fatal_missing_validations));
 
   if (!caps->IsValid()) {
     VALIDATION_LOG << "Could not determine device capabilities.";