make context() virtual on device

src/core/SkCanvas.cpp

Index: src/core/SkCanvas.cpp
diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index 3924260f809468a77d45bd93ae6264ec56af3572..905849254c7fcf5ad6689fe9354cc326ff395992 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -1863,18 +1863,8 @@ GrRenderTarget* SkCanvas::internal_private_accessTopLayerRenderTarget() {
 }
 
 GrContext* SkCanvas::getGrContext() {
-#if SK_SUPPORT_GPU
     SkBaseDevice* device = this->getTopDevice();
-    if (device) {
-        GrRenderTarget* renderTarget = device->accessRenderTarget();
-        if (renderTarget) {
-            return renderTarget->getContext();
-        }
-    }
-#endif
-
-    return nullptr;
-
+    return device ? device->context() : nullptr;
 }
 
 void SkCanvas::drawDRRect(const SkRRect& outer, const SkRRect& inner,