Enable SkiaPipelines to interoperate with existing GlesDriver configs.

Test: hwui unit tests
Change-Id: Icd94d0e21130d86fb5514801f999d0018a69e151
diff --git a/libs/hwui/debug/NullGlesDriver.h b/libs/hwui/debug/NullGlesDriver.h
index d731379..37ca8f34 100644
--- a/libs/hwui/debug/NullGlesDriver.h
+++ b/libs/hwui/debug/NullGlesDriver.h
@@ -24,6 +24,8 @@
 
 class NullGlesDriver : public FatalBaseDriver {
 public:
+    virtual sk_sp<const GrGLInterface> getSkiaInterface() override;
+
     virtual void glGenBuffers_(GLsizei n, GLuint *buffers) override;
     virtual void glGenFramebuffers_(GLsizei n, GLuint *framebuffers) override;
     virtual void glGenRenderbuffers_(GLsizei n, GLuint *renderbuffers) override;