Add config options to run different GPU APIs to dm and nanobench

include/gpu/gl/SkNullGLContext.h

Index: include/gpu/gl/SkNullGLContext.h
diff --git a/include/gpu/gl/SkNullGLContext.h b/include/gpu/gl/SkNullGLContext.h
index 1f634382641ec02dd336304f754a80c1ac78b5e2..9e799a9fea4d9d7b9b832026f4c664aee7a797ec 100644
--- a/include/gpu/gl/SkNullGLContext.h
+++ b/include/gpu/gl/SkNullGLContext.h
@@ -14,7 +14,12 @@ class SK_API SkNullGLContext : public SkGLContext {
 public:
     ~SkNullGLContext() override;
 
-    static SkNullGLContext* Create(GrGLStandard);
+    static SkNullGLContext* Create();
+    // FIXME: remove once Chromium has been updated.
+    static SkNullGLContext* Create(GrGLStandard forcedAPI) {
+        SkASSERT(forcedAPI == kNone_GrGLStandard);
+        (void)forcedAPI;        return Create();
+    }
 
     class ContextState;