Deprecate access to non-public Suite and Spec members via Env#topSuite

The deprecation warning relies on Proxy, and won't work in environments
that don't have it. Among Jasmine's supported environments, that's Safari 9,
Safari 8, and all versions of IE.

src/core/deprecatingSpecProxy.js

@@ -0,0 +1,70 @@
+/* eslint-disable compat/compat */
+// TODO: Remove this in the next major release.
+getJasmineRequireObj().deprecatingSpecProxy = function(j$) {
+  function isMember(target, prop) {
+    return (
+      Object.keys(target).indexOf(prop) !== -1 ||
+      Object.keys(j$.Spec.prototype).indexOf(prop) !== -1
+    );
+  }
+
+  function isAllowedMember(prop) {
+    return prop === 'description' || prop === 'getFullName';
+  }
+
+  function msg(member) {
+    var memberName = member.toString().replace(/^Symbol\((.+)\)$/, '$1');
+    return (
+      'Access to private Spec members (in this case `' +
+      memberName +
+      '`) via Env#topSuite is not supported and will break in ' +
+      'a future release. See <https://jasmine.github.io/api/edge/Spec.html> ' +
+      'for correct usage.'
+    );
+  }
+
+  try {
+    new Proxy({}, {});
+  } catch (e) {
+    // Environment does not support Poxy.
+    return function(spec) {
+      return spec;
+    };
+  }
+
+  function DeprecatingSpecProxyHandler(env) {
+    this._env = env;
+  }
+
+  DeprecatingSpecProxyHandler.prototype.get = function(target, prop, receiver) {
+    this._maybeDeprecate(target, prop);
+
+    if (prop === 'getFullName') {
+      // getFullName calls a private method. Re-bind 'this' to avoid a bogus
+      // deprecation warning.
+      return target.getFullName.bind(target);
+    } else {
+      return target[prop];
+    }
+  };
+
+  DeprecatingSpecProxyHandler.prototype.set = function(target, prop, value) {
+    this._maybeDeprecate(target, prop);
+    return (target[prop] = value);
+  };
+
+  DeprecatingSpecProxyHandler.prototype._maybeDeprecate = function(
+    target,
+    prop
+  ) {
+    if (isMember(target, prop) && !isAllowedMember(prop)) {
+      this._env.deprecated(msg(prop));
+    }
+  };
+
+  function deprecatingSpecProxy(spec, env) {
+    return new Proxy(spec, new DeprecatingSpecProxyHandler(env));
+  }
+
+  return deprecatingSpecProxy;
+};