layers: Some simple style tweaks for swapchain
layers: Some simple style tweaks for swapchain

Fixed some variable names and removed c-style casts.

Change-Id: I994ca311665a59d0f81ce0cfdeda4a66deb632be

elongbug/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,elongbug/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,elongbug/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,elongbug/Vulkan-LoaderAndValidationLayers