Move SkiaGpuContext creation in SkiaVkRenderEngine to virtual function

Making GaneshVkRenderEngine / GraphiteVkRenderEngine handle this reduces
the need for higher-level branching.

Test: boots successfully with skiavkthreaded
Bug: b/293371537
Change-Id: I5685cb9dd7b0dc1ce3a2d538a729c255fbd6c52b
diff --git a/libs/renderengine/skia/SkiaVkRenderEngine.h b/libs/renderengine/skia/SkiaVkRenderEngine.h
index 3f40e3d..371b812 100644
--- a/libs/renderengine/skia/SkiaVkRenderEngine.h
+++ b/libs/renderengine/skia/SkiaVkRenderEngine.h
@@ -71,6 +71,7 @@
     };
 
 protected:
+    virtual std::unique_ptr<SkiaGpuContext> createContext(VulkanInterface& vulkanInterface) = 0;
     // Redeclare parent functions that Ganesh vs. Graphite subclasses must implement.
     virtual void waitFence(SkiaGpuContext* context, base::borrowed_fd fenceFd) override = 0;
     virtual base::unique_fd flushAndSubmit(SkiaGpuContext* context,