Added the Vulkan Context Provider implementation.

cc/output/vulkan_in_process_context_provider.h

Index: cc/output/vulkan_in_process_context_provider.h
diff --git a/cc/output/vulkan_in_process_context_provider.h b/cc/output/vulkan_in_process_context_provider.h
index 3f3de6161e621a71da7258650f2653420e59bef5..c477f2f3eee20c233393ce79346f8d52188a52c9 100644
--- a/cc/output/vulkan_in_process_context_provider.h
+++ b/cc/output/vulkan_in_process_context_provider.h
@@ -23,6 +23,7 @@ class CC_EXPORT VulkanInProcessContextProvider : public VulkanContextProvider {
   bool Initialize();
   void Destroy();
 
+  // VulkanContextProvider implementation
   gpu::VulkanDeviceQueue* GetDeviceQueue() override;
 
  protected:
@@ -30,7 +31,11 @@ class CC_EXPORT VulkanInProcessContextProvider : public VulkanContextProvider {
   ~VulkanInProcessContextProvider() override;
 
  private:
+#if defined(ENABLE_VULKAN)
   std::unique_ptr<gpu::VulkanDeviceQueue> device_queue_;
+#endif
+
+  DISALLOW_COPY_AND_ASSIGN(VulkanInProcessContextProvider);
 };
 
 }  // namespace cc