Add OpenGL context to Viewer.

tools/viewer/sk_app/VulkanWindowContext.cpp

Index: tools/viewer/sk_app/VulkanWindowContext.cpp
diff --git a/tools/viewer/sk_app/VulkanWindowContext.cpp b/tools/viewer/sk_app/VulkanWindowContext.cpp
index 2570e826a387c873afa3529bc95bb968814a4173..cee9ec73a6d6087c597de57c68ebcd0c515fcd9b 100644
--- a/tools/viewer/sk_app/VulkanWindowContext.cpp
+++ b/tools/viewer/sk_app/VulkanWindowContext.cpp
@@ -25,8 +25,12 @@
 namespace sk_app {
 
 VulkanWindowContext::VulkanWindowContext(void* platformData, const DisplayParams& params)
-    : fSurface(VK_NULL_HANDLE)
+    : WindowContext()
+    , fSurface(VK_NULL_HANDLE)
     , fSwapchain(VK_NULL_HANDLE)
+    , fImages(nullptr)
+    , fImageLayouts(nullptr)
+    , fSurfaces(nullptr)
     , fCommandPool(VK_NULL_HANDLE)
     , fBackbuffers(nullptr) {
 
@@ -269,6 +273,7 @@ void VulkanWindowContext::createBuffers(VkFormat format) {
         desc.fSampleCnt = 0;
         desc.fStencilBits = 0;
         desc.fRenderTargetHandle = (GrBackendObject) &info;
+        // TODO: base this on fSurfaceProps
         SkSurfaceProps props(GrPixelConfigIsSRGB(fPixelConfig)
                              ? SkSurfaceProps::kGammaCorrect_Flag : 0,
                              kUnknown_SkPixelGeometry);
@@ -398,7 +403,8 @@ void VulkanWindowContext::destroyContext() {
         fSurface = VK_NULL_HANDLE;
     }
 
-    delete fContext;
+    fContext->abandonContext();
+    fContext->unref();
 
     fBackendContext.reset(nullptr);
 }
@@ -419,7 +425,7 @@ VulkanWindowContext::BackbufferInfo* VulkanWindowContext::getAvailableBackbuffer
     return backbuffer;
 }
 
-SkSurface* VulkanWindowContext::getBackbufferSurface() {
+sk_sp<SkSurface> VulkanWindowContext::getBackbufferSurface() {
     BackbufferInfo* backbuffer = this->getAvailableBackbuffer();
     SkASSERT(backbuffer);
 
@@ -510,10 +516,9 @@ SkSurface* VulkanWindowContext::getBackbufferSurface() {
                         QueueSubmit(fBackendContext->fQueue, 1, &submitInfo,
                                     backbuffer->fUsageFences[0]));
 
-    return fSurfaces[backbuffer->fImageIndex].get();
+    return sk_ref_sp(fSurfaces[backbuffer->fImageIndex].get());
 }
 
-
 void VulkanWindowContext::swapBuffers() {
 
     BackbufferInfo* backbuffer = fBackbuffers + fCurrentBackbufferIndex;