Add OpenGL context to Viewer.

tools/viewer/sk_app/Window.cpp

 /*
 * Copyright 2016 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
 #include "Window.h"
 
 #include "SkSurface.h"
@@ skipping 45 matching lines @@
 
 bool Window::onMouse(int x, int y, InputState state, uint32_t modifiers) {
     return fMouseFunc(x, y, state, modifiers, fMouseUserData);
 }
 
 bool Window::onTouch(int owner, InputState state, float x, float y) {
     return fTouchFunc(owner, state, x, y, fTouchUserData);
 }
 
 void Window::onPaint() {
-    SkSurface* backbuffer = fWindowContext->getBackbufferSurface();
+    sk_sp<SkSurface> backbuffer = fWindowContext->getBackbufferSurface();
     if (backbuffer) {
         // draw into the canvas of this surface
         SkCanvas* canvas = backbuffer->getCanvas();
 
         fPaintFunc(canvas, fPaintUserData);
 
         canvas->flush();
 
         fWindowContext->swapBuffers();
     } else {
         // try recreating testcontext
     }
-
 }
 
 void Window::onResize(uint32_t w, uint32_t h) {
     fWidth = w;
     fHeight = h;
     fWindowContext->resize(w, h);
 }
 
 const DisplayParams& Window::getDisplayParams() {
     return fWindowContext->getDisplayParams();
 }
 
 void Window::setDisplayParams(const DisplayParams& params) {
     fWindowContext->setDisplayParams(params);
 }
 
 }   // namespace sk_app