Remove unused member in VulkanManager.

A large part of the previous change was specifically around removing
this ref counted data member, and then I just forgot to delete it...

Test: manual testing

Change-Id: Ie9a7f7495789d45a65900c08a27a9d83ad64617c
diff --git a/libs/hwui/renderthread/VulkanManager.h b/libs/hwui/renderthread/VulkanManager.h
index 2a1b36f..9a72706 100644
--- a/libs/hwui/renderthread/VulkanManager.h
+++ b/libs/hwui/renderthread/VulkanManager.h
@@ -79,7 +79,7 @@
     void initialize();
 
     // Quick check to see if the VulkanManager has been initialized.
-    bool hasVkContext() { return mBackendContext.get() != nullptr; }
+    bool hasVkContext() { return mDevice != VK_NULL_HANDLE; }
 
     // Given a window this creates a new VkSurfaceKHR and VkSwapchain and stores them inside a new
     // VulkanSurface object which is returned.
@@ -188,8 +188,6 @@
 
     RenderThread& mRenderThread;
 
-    sk_sp<const GrVkBackendContext> mBackendContext;
-
     VkInstance mInstance = VK_NULL_HANDLE;
     VkPhysicalDevice mPhysicalDevice = VK_NULL_HANDLE;
     VkDevice mDevice = VK_NULL_HANDLE;