Remove goog.asserts.*

This pull requests replaces type check hint assertions with type casts,
library sanity check assertions with conditional console.assert statements
in debug mode, and runtime sanity checks with assertions that throw an
ol.AssertionError with an error code for lookup outside the library.

test/spec/ol/ol.test.js

@@ -0,0 +1,37 @@
+goog.provide('ol.test');
+
+describe('ol', function() {
+
+  describe('ol.assert', function() {
+    it('throws an exception', function() {
+      expect(function() {
+        ol.assert(false, 42);
+      }).to.throwException();
+    });
+  });
+
+  describe('ol.AssertionError', function() {
+    it('generates a message', function() {
+      var error = new ol.AssertionError(42);
+      expect(error.message).to.be('Assertion failed. See /doc/errors.html#42 for details.');
+    });
+    it('generates a message with a versioned url', function() {
+      var origVersion = ol.VERSION;
+      ol.VERSION = 'foo';
+      var error = new ol.AssertionError(42);
+      expect(error.message).to.be('Assertion failed. See http://openlayers.org/en/foo/doc/errors.html#42 for details.');
+      ol.VERSION = origVersion;
+    });
+    it('has an error code', function() {
+      var error = new ol.AssertionError(42);
+      expect(error.code).to.be(42);
+    });
+    it('has a name', function() {
+      var error = new ol.AssertionError(42);
+      expect(error.name).to.be('AssertionError');
+    })
+  });
+
+});
+
+goog.require('ol');