Use Offscreen Surface for Split Screen

tools/viewer/sk_app/WindowContext.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #ifndef WindowContext_DEFINED
 #define WindowContext_DEFINED
 
 #include "DisplayParams.h"
@@ skipping 26 matching lines @@
     virtual void setDisplayParams(const DisplayParams& params) = 0;
 
     SkSurfaceProps getSurfaceProps() const { return fSurfaceProps; }
     void setSurfaceProps(const SkSurfaceProps& props) {
         fSurfaceProps = props;
     }
 
     virtual GrBackendContext getBackendContext() = 0;
     GrContext* getGrContext() const { return fContext; }
 
+    sk_sp<SkSurface> createOffscreenSurface(bool sRGB);
     sk_sp<SkSurface> createRenderSurface(sk_sp<GrRenderTarget>, int colorBits);
     void presentRenderSurface(sk_sp<SkSurface> renderSurface, sk_sp<GrRenderTarget> rt,
                               int colorBits);
 
 protected:
     virtual bool isGpuContext() { return true;  }
 
     GrContext*        fContext;
 
     int               fWidth;
     int               fHeight;
     DisplayParams     fDisplayParams;
     GrPixelConfig     fPixelConfig;
     SkSurfaceProps    fSurfaceProps;
+
+private:
+    sk_sp<SkSurface> createSurface(
+            sk_sp<GrRenderTarget>, int colorBits, bool offscreen, bool forceSRGB);
 };
 
 }   // namespace sk_app
 
 #endif