vulkan: Add skeleton swapchain support

Loader and driver entry points exist and the call chains are hooked up
properly, but functions are just empty stubs for now.

Change-Id: I6ff95e47d1d09ebed41eda8accb71686c8249546
(cherry picked from commit 038c8a740bbda4650bec776023a26a7fcbf93864)
diff --git a/vulkan/nulldrv/null_driver.h b/vulkan/nulldrv/null_driver.h
index c6c7aa6..6bfbda5 100644
--- a/vulkan/nulldrv/null_driver.h
+++ b/vulkan/nulldrv/null_driver.h
@@ -19,6 +19,7 @@
 
 #define VK_PROTOTYPES
 #include <vulkan/vulkan.h>
+#include <vulkan/vk_ext_android_native_buffer.h>
 
 namespace null_driver {
 
@@ -177,6 +178,9 @@
 void CmdNextSubpass(VkCmdBuffer cmdBuffer, VkRenderPassContents contents);
 void CmdEndRenderPass(VkCmdBuffer cmdBuffer);
 void CmdExecuteCommands(VkCmdBuffer cmdBuffer, uint32_t cmdBuffersCount, const VkCmdBuffer* pCmdBuffers);
+
+VkResult ImportNativeFenceANDROID(VkDevice device, VkSemaphore semaphore, int nativeFenceFd);
+VkResult QueueSignalNativeFenceANDROID(VkQueue queue, int* pNativeFenceFd);
 // clang-format on
 
 }  // namespace null_driver