Import new functionality for GL4 backend

src/gpu/gl/SkNullGLContext.cpp

Index: src/gpu/gl/SkNullGLContext.cpp
diff --git a/src/gpu/gl/SkNullGLContext.cpp b/src/gpu/gl/SkNullGLContext.cpp
index cf07cb3ca260898d35ccafcc0cdc8ad04a5d1fe7..7ced85e89e2d12ccbb0091eb9c4321c437f00f16 100644
--- a/src/gpu/gl/SkNullGLContext.cpp
+++ b/src/gpu/gl/SkNullGLContext.cpp
@@ -385,9 +385,11 @@ static GrGLInterface* create_null_interface(State* state) {
     functions->fDisable = noOpGLDisable;
     functions->fDisableVertexAttribArray = noOpGLDisableVertexAttribArray;
     functions->fDrawArrays = noOpGLDrawArrays;
+    functions->fDrawArraysInstanced = noOpGLDrawArraysInstanced;
     functions->fDrawBuffer = noOpGLDrawBuffer;
     functions->fDrawBuffers = noOpGLDrawBuffers;
     functions->fDrawElements = noOpGLDrawElements;
+    functions->fDrawElementsInstanced = noOpGLDrawElementsInstanced;
     functions->fEnable = noOpGLEnable;
     functions->fEnableVertexAttribArray = noOpGLEnableVertexAttribArray;
     functions->fEndQuery = noOpGLEndQuery;
@@ -467,6 +469,7 @@ static GrGLInterface* create_null_interface(State* state) {
     functions->fVertexAttrib3fv = noOpGLVertexAttrib3fv;
     functions->fVertexAttrib4fv = noOpGLVertexAttrib4fv;
     functions->fVertexAttribPointer = noOpGLVertexAttribPointer;
+    functions->fVertexAttribDivisor = noOpGLVertexAttribDivisor;
     functions->fViewport = nullGLViewport;
     functions->fBindFramebuffer = nullGLBindFramebuffer;
     functions->fBindRenderbuffer = nullGLBindRenderbuffer;