gpu: vulkan: Add missing VULKAN_EXPORT to VulkanCommandPool

Bug: none
Test: compile ozone_demo with is_component_build=true

Change-Id: Icf24cfcb5c3737d9f51136da73a9bc593937f813
Reviewed-on: https://chromium-review.googlesource.com/1146981
Commit-Queue: Michael Spang <spang@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577542}

gpu/vulkan/vulkan_command_pool.h

@@ -10,13 +10,14 @@
 #include <memory>
 
 #include "base/macros.h"
+#include "gpu/vulkan/vulkan_export.h"
 
 namespace gpu {
 
 class VulkanCommandBuffer;
 class VulkanDeviceQueue;
 
-class VulkanCommandPool {
+class VULKAN_EXPORT VulkanCommandPool {
  public:
   explicit VulkanCommandPool(VulkanDeviceQueue* device_queue);
   ~VulkanCommandPool();