URLPattern: Implement compare() method.

This CL adds a prototype URLPattern.compareComponent() to provide a
natural ordering to URLPattern pattern strings.  This was based on
feedback from routing framework authors and there is some discussion
in:

whatwg/urlpattern#61

The general algorithm is to compare the component patterns Part by Part.
The PartType, Modifier, and text contents are compared for each Part,
but group names are not considered.  The end result is a mostly
lexicographical ordering based on fixed text.  Matching groups and
modifiers are ordered such that more restrictive patterns are greater.

Bug: 1232795
Change-Id: I8474cd7d7689e657c9c74c552ad630cdcdd86c95

urlpattern/resources/urlpattern-compare-test-data.json

@@ -0,0 +1,110 @@
+[
+  {
+    "component": "pathname",
+    "left": { "pathname": "/foo/a" },
+    "right": { "pathname": "/foo/b" },
+    "expected": -1
+  },
+  {
+    "component": "pathname",
+    "left": { "pathname": "/foo/b" },
+    "right": { "pathname": "/foo/bar" },
+    "expected": -1
+  },
+  {
+    "component": "pathname",
+    "left": { "pathname": "/foo/bar" },
+    "right": { "pathname": "/foo/:bar" },
+    "expected": 1
+  },
+  {
+    "component": "pathname",
+    "left": { "pathname": "/foo/" },
+    "right": { "pathname": "/foo/:bar" },
+    "expected": 1
+  },
+  {
+    "component": "pathname",
+    "left": { "pathname": "/foo/:bar" },
+    "right": { "pathname": "/foo/*" },
+    "expected": 1
+  },
+  {
+    "component": "pathname",
+    "left": { "pathname": "/foo/{bar}" },
+    "right": { "pathname": "/foo/(bar)" },
+    "expected": 1
+  },
+  {
+    "component": "pathname",
+    "left": { "pathname": "/foo/{bar}" },
+    "right": { "pathname": "/foo/{bar}+" },
+    "expected": 1
+  },
+  {
+    "component": "pathname",
+    "left": { "pathname": "/foo/{bar}+" },
+    "right": { "pathname": "/foo/{bar}?" },
+    "expected": 1
+  },
+  {
+    "component": "pathname",
+    "left": { "pathname": "/foo/{bar}?" },
+    "right": { "pathname": "/foo/{bar}*" },
+    "expected": 1
+  },
+  {
+    "component": "pathname",
+    "left": { "pathname": "/foo/(123)" },
+    "right": { "pathname": "/foo/(12)" },
+    "expected": 1
+  },
+  {
+    "component": "pathname",
+    "left": { "pathname": "/foo/:b" },
+    "right": { "pathname": "/foo/:a" },
+    "expected": 0
+  },
+  {
+    "component": "pathname",
+    "left": { "pathname": "*/foo" },
+    "right": { "pathname": "*" },
+    "expected": 1
+  },
+  {
+    "component": "port",
+    "left": { "port": "9" },
+    "right": { "port": "100" },
+    "expected": 1
+  },
+  {
+    "component": "pathname",
+    "left": { "pathname": "foo/:bar?/baz" },
+    "right": { "pathname": "foo/{:bar}?/baz" },
+    "expected": -1
+  },
+  {
+    "component": "pathname",
+    "left": { "pathname": "foo/:bar?/baz" },
+    "right": { "pathname": "foo{/:bar}?/baz" },
+    "expected": 0
+  },
+  {
+    "component": "pathname",
+    "left": { "pathname": "foo/:bar?/baz" },
+    "right": { "pathname": "fo{o/:bar}?/baz" },
+    "expected": 1
+  },
+  {
+    "component": "pathname",
+    "left": { "pathname": "foo/:bar?/baz" },
+    "right": { "pathname": "foo{/:bar/}?baz" },
+    "expected": -1
+  },
+  {
+    "component": "pathname",
+    "left": "https://a.example.com/b?a",
+    "right": "https://b.example.com/a?b",
+    "expected": 1
+  }
+]

urlpattern/resources/urlpattern-compare-tests.js

@@ -0,0 +1,26 @@
+function runTests(data) {
+  for (let entry of data) {
+    test(function() {
+      const left = new URLPattern(entry.left);
+      const right = new URLPattern(entry.right);
+
+      assert_equals(URLPattern.compareComponent(entry.component, left, right), entry.expected);
+
+      // We have to coerce to an integer here in order to avoid asserting
+      // that `+0` is `-0`.
+      const reverse_expected = ~~(entry.expected * -1);
+      assert_equals(URLPattern.compareComponent(entry.component, right, left), reverse_expected, "reverse order");
+
+      assert_equals(URLPattern.compareComponent(entry.component, left, left), 0, "left equality");
+      assert_equals(URLPattern.compareComponent(entry.component, right, right), 0, "right equality");
+    }, `Component: ${entry.component} ` +
+       `Left: ${JSON.stringify(entry.left)} ` +
+       `Right: ${JSON.stringify(entry.right)}`);
+  }
+}
+
+promise_test(async function() {
+  const response = await fetch('resources/urlpattern-compare-test-data.json');
+  const data = await response.json();
+  runTests(data);
+}, 'Loading data...');

urlpattern/urlpattern-compare.any.js

@@ -0,0 +1,2 @@
+// META: global=window,worker
+// META: script=resources/urlpattern-compare-tests.js

urlpattern/urlpattern-compare.https.any.js

@@ -0,0 +1,2 @@
+// META: global=window,worker
+// META: script=resources/urlpattern-compare-tests.js