Move GrGLInterface function pointers into a nested struct

src/gpu/gl/GrGLUniformManager.cpp

Index: src/gpu/gl/GrGLUniformManager.cpp
diff --git a/src/gpu/gl/GrGLUniformManager.cpp b/src/gpu/gl/GrGLUniformManager.cpp
index 674118b7491da615b2ecdae646cc51b8baa6e423..29679aa409a4c07308fb972f53a45fe268eb8d6b 100644
--- a/src/gpu/gl/GrGLUniformManager.cpp
+++ b/src/gpu/gl/GrGLUniformManager.cpp
@@ -16,7 +16,8 @@
                   (1 == arrayCount && GrGLShaderVar::kNonArray == uni.fArrayCount))
 
 GrGLUniformManager::GrGLUniformManager(GrGpuGL* gpu) : fGpu(gpu) {
-    fUsingBindUniform = fGpu->glInterface()->fBindUniformLocation != NULL;
+    // skbug.com/2056
+    fUsingBindUniform = fGpu->glInterface()->fFunctions.fBindUniformLocation != NULL;
 }
 
 GrGLUniformManager::UniformHandle GrGLUniformManager::appendUniform(GrSLType type, int arrayCount) {