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 0140477a54db55742d459d3714ab76557c16d4b8..16b42a4ea18f44f76cdb445d41db4ce19297f74d 100644
--- a/tools/gpu/gl/angle/GLTestContext_angle.h
+++ b/tools/gpu/gl/angle/GLTestContext_angle.h
@@ -18,13 +18,19 @@ namespace sk_gpu_test {
  */
 const GrGLInterface* CreateANGLEGLInterface();
 
-#ifdef SK_BUILD_FOR_WIN
-/** Creates a GLTestContext backed by ANGLE's Direct3D backend. */
-GLTestContext* CreateANGLEDirect3DGLTestContext();
-#endif
+enum class ANGLEBackend {
+    kD3D9,
+    kD3D11,
+    kOpenGL
+};
+
+enum class ANGLEContextVersion {
+    kES2,
+    kES3
+};
 
-/** Creates a GLTestContext backed by ANGLE's OpenGL backend. */
-GLTestContext* CreateANGLEOpenGLGLTestContext();
+/** Creates a GLTestContext backed by ANGLE. */
+GLTestContext* CreateANGLETestContext(ANGLEBackend, ANGLEContextVersion);
 
 }  // namespace sk_gpu_test
 #endif