[vulkan] Plumb IOStream to VulkanStream

bug: 111137294

and implement actual read/write

Change-Id: Ia1c6ae45518f35783f0d055e086988944845d10c
diff --git a/system/vulkan_enc/VkEncoder.h b/system/vulkan_enc/VkEncoder.h
index 4ea28e2..2278082 100644
--- a/system/vulkan_enc/VkEncoder.h
+++ b/system/vulkan_enc/VkEncoder.h
@@ -16,12 +16,17 @@
 #ifdef GOLDFISH_VULKAN
 #pragma once
 
-#include "IOStream.h"
+#include <memory>
+
+class IOStream;
 
 class VkEncoder {
 public:
-    VkEncoder(IOStream*) { }
-    ~VkEncoder() { }
+    VkEncoder(IOStream* stream);
+    ~VkEncoder();
+private:
+    class Impl;
+    std::unique_ptr<Impl> mImpl;
 };
 
 #else