Revert of Explicit control in tools of ANGLE frontend and backend

tools/gpu/gl/angle/GLTestContext_angle.h

Index: tools/gpu/gl/angle/GLTestContext_angle.h
diff --git a/tools/gpu/gl/angle/GLTestContext_angle.h b/tools/gpu/gl/angle/GLTestContext_angle.h
index 0da747f30f5a237ee7721b96e7d566c2f78e535f..0140477a54db55742d459d3714ab76557c16d4b8 100644
--- a/tools/gpu/gl/angle/GLTestContext_angle.h
+++ b/tools/gpu/gl/angle/GLTestContext_angle.h
@@ -13,24 +13,18 @@
 namespace sk_gpu_test {
 
 /**
- * Creates a GrGLInterface for the current ANGLE GLES Context. Here current means bound in ANGLE's
- * implementation of EGL.
+ * Creates a GrGLInterface for the currently ANGLE GL context currently bound in ANGLE's EGL
+ * implementation.
  */
 const GrGLInterface* CreateANGLEGLInterface();
 
-enum class ANGLEBackend {
-    kD3D9,
-    kD3D11,
-    kOpenGL
-};
+#ifdef SK_BUILD_FOR_WIN
+/** Creates a GLTestContext backed by ANGLE's Direct3D backend. */
+GLTestContext* CreateANGLEDirect3DGLTestContext();
+#endif
 
-enum class ANGLEContextVersion {
-    kES2,
-    kES3
-};
-
-/** Creates a GLTestContext backed by ANGLE. */
-GLTestContext* CreateANGLETestContext(ANGLEBackend, ANGLEContextVersion);
+/** Creates a GLTestContext backed by ANGLE's OpenGL backend. */
+GLTestContext* CreateANGLEOpenGLGLTestContext();
 
 }  // namespace sk_gpu_test
 #endif