Add API for custom handling of deprecations

spec/api-deprecations-spec.js

@@ -0,0 +1,27 @@
+const assert = require('assert');
+const deprecations = require('electron').deprecations;
+
+describe('deprecations', function() {
+  beforeEach(function() {
+    deprecations.setHandler(null);
+    process.throwDeprecation = true;
+  });
+
+  it('allows a deprecation handler function to be specified', function() {
+    var messages = [];
+
+    deprecations.setHandler(function (message) {
+      messages.push(message)
+    });
+
+    require('electron').webFrame.registerUrlSchemeAsSecure('some-scheme')
+
+    assert.deepEqual(messages, ['registerUrlSchemeAsSecure is deprecated. Use registerURLSchemeAsSecure instead.']);
+  });
+
+  it('throws an exception if no deprecation handler is specified', function() {
+    assert.throws(function() {
+      require('electron').webFrame.registerUrlSchemeAsPrivileged('some-scheme')
+    }, "registerUrlSchemeAsPrivileged is deprecated. Use registerURLSchemeAsPrivileged instead.");
+  });
+})