Remove unused functions from GrGLVertexBuffer / IndexBuffer

BUG=skia:

Review URL: https://codereview.chromium.org/1416303002
diff --git a/src/gpu/gl/GrGLIndexBuffer.h b/src/gpu/gl/GrGLIndexBuffer.h
index 62abb0c..628970a 100644
--- a/src/gpu/gl/GrGLIndexBuffer.h
+++ b/src/gpu/gl/GrGLIndexBuffer.h
@@ -24,12 +24,6 @@
     GrGLuint bufferID() const { return fImpl.bufferID(); }
     size_t baseOffset() const { return fImpl.baseOffset(); }
 
-    void bind() const {
-        if (!this->wasDestroyed()) {
-            fImpl.bind(this->getGpuGL());
-        }
-    }
-
 protected:
     void onAbandon() override;
     void onRelease() override;
diff --git a/src/gpu/gl/GrGLVertexBuffer.h b/src/gpu/gl/GrGLVertexBuffer.h
index bc68534..93c6b2b 100644
--- a/src/gpu/gl/GrGLVertexBuffer.h
+++ b/src/gpu/gl/GrGLVertexBuffer.h
@@ -24,12 +24,6 @@
     GrGLuint bufferID() const { return fImpl.bufferID(); }
     size_t baseOffset() const { return fImpl.baseOffset(); }
 
-    void bind() const {
-        if (!this->wasDestroyed()) {
-            fImpl.bind(this->getGpuGL());
-        }
-    }
-
 protected:
     void onAbandon() override;
     void onRelease() override;