Add OpenGL context to Viewer.

tools/viewer/sk_app/VulkanWindowContext.h

Index: tools/viewer/sk_app/VulkanWindowContext.h
diff --git a/tools/viewer/sk_app/VulkanWindowContext.h b/tools/viewer/sk_app/VulkanWindowContext.h
index ec80a3251d2f080c17b6d8dd7c1acf34b922b740..8480a9efa83f31e94dc483569114173d3002cae2 100644
--- a/tools/viewer/sk_app/VulkanWindowContext.h
+++ b/tools/viewer/sk_app/VulkanWindowContext.h
@@ -13,8 +13,7 @@
 #include "vk/GrVkBackendContext.h"
 #include "WindowContext.h"
 
-class SkSurface;
-class GrContext;
+class GrRenderTarget;
 
 namespace sk_app {
 
@@ -35,18 +34,15 @@ public:
         return ctx;
     }
 
-    SkSurface* getBackbufferSurface() override;
+    sk_sp<SkSurface> getBackbufferSurface() override;
     void swapBuffers() override;
 
-    bool makeCurrent() override { return true; }
-
     bool isValid() override { return SkToBool(fBackendContext.get()); }
 
     void resize(uint32_t w, uint32_t h) override {
         this->createSwapchain(w, h, fDisplayParams);
     }
 
-    const DisplayParams& getDisplayParams() override { return fDisplayParams; }
     void setDisplayParams(const DisplayParams& params) override {
         this->createSwapchain(fWidth, fHeight, params);
     }
@@ -99,23 +95,21 @@ private:
     VkPtr<PFN_vkQueuePresentKHR> fQueuePresentKHR;
     VkPtr<PFN_vkCreateSharedSwapchainsKHR> fCreateSharedSwapchainsKHR;
 
-    GrContext*        fContext;
     VkSurfaceKHR      fSurface;
     VkSwapchainKHR    fSwapchain;
     uint32_t          fPresentQueueIndex;
     VkQueue           fPresentQueue;
     int               fWidth;
     int               fHeight;
-    DisplayParams     fDisplayParams;
-    GrPixelConfig     fPixelConfig;
-
-    uint32_t          fImageCount;
-    VkImage*          fImages;         // images in the swapchain
-    VkImageLayout*    fImageLayouts;   // layouts of these images when not color attachment
-    sk_sp<SkSurface>* fSurfaces;       // wrapped surface for those images
-    VkCommandPool     fCommandPool;
-    BackbufferInfo*   fBackbuffers;
-    uint32_t          fCurrentBackbufferIndex;
+
+    uint32_t               fImageCount;
+    VkImage*               fImages;         // images in the swapchain
+    VkImageLayout*         fImageLayouts;   // layouts of these images when not color attachment
+    sk_sp<GrRenderTarget>* fRenderTargets;  // wrapped rendertargets for those images
+    sk_sp<SkSurface>*      fSurfaces;       // surfaces client renders to (may not be based on rts)
+    VkCommandPool          fCommandPool;
+    BackbufferInfo*        fBackbuffers;
+    uint32_t               fCurrentBackbufferIndex;
 };
 
 }   // namespace sk_app