Make unit tests use generic testcontext rather than glcontext

tools/gpu/GrContextFactory.h

Index: tools/gpu/GrContextFactory.h
diff --git a/tools/gpu/GrContextFactory.h b/tools/gpu/GrContextFactory.h
index dc896a7bc8be32083cb399fa464807b2191b4594..ed8e6451999514aa001fb0870754a24b36282cd8 100644
--- a/tools/gpu/GrContextFactory.h
+++ b/tools/gpu/GrContextFactory.h
@@ -28,6 +28,8 @@ public:
 
     GrContext* grContext() const { return fGrContext; }
 
+    TestContext* testContext() const { return fTestContext; }
+
     GLTestContext* glContext() const {
         SkASSERT(kOpenGL_GrBackend == fBackend);
         return static_cast<GLTestContext*>(fTestContext);
@@ -93,6 +95,18 @@ public:
         kRequireSRGBSupport_ContextOptions  = 0x2,
     };
 
+    static ContextType NativeContextTypeForBackend(GrBackend backend) {
+        switch (backend) {
+            case kOpenGL_GrBackend:
+                return kNativeGL_ContextType;
+            case kVulkan_GrBackend:
+                return kVulkan_ContextType;
+            default:
+                SkFAIL("Unknown backend");
+                return kNullGL_ContextType;
+        }
+    }
+
     static bool IsRenderingContext(ContextType type) {
         switch (type) {
             case kNullGL_ContextType: