Add angle config to nanobench and make angle a default config for dm and nanobench.

bench/nanobench.cpp

Index: bench/nanobench.cpp
diff --git a/bench/nanobench.cpp b/bench/nanobench.cpp
index 2dfd33f594abea06cf4034dc34ffcafc0b7687a4..c808183b194d57d9a1ed5ebd1e12f5b41a2bc5c5 100644
--- a/bench/nanobench.cpp
+++ b/bench/nanobench.cpp
@@ -282,6 +282,9 @@ static void create_configs(SkTDArray<Config>* configs) {
         GPU_CONFIG(nvprmsaa16, kNVPR_GLContextType, 16)
         GPU_CONFIG(debug, kDebug_GLContextType, 0)
         GPU_CONFIG(nullgpu, kNull_GLContextType, 0)
+#ifdef SK_ANGLE
+        GPU_CONFIG(angle, kANGLE_GLContextType, 0)
+#endif
     }
 #endif
 }