added hook function to appIntegration to handle function-overwrites from other extensions

chrome/content/tests/tests/hooks.js

+(function()
+{
+  let {hook} = require("hooks");
+
+  let results = [];
+  let gBrowser = null;
+
+  module("Function hooks",
+  {
+    setup: function()
+    {
+      gBrowser = new (function()
+      {
+        this.foo = function(value)
+        {
+          results.push(value);
+        }
+      })();
+    },
+    teardown: function()
+    {
+      results = [];
+      gBrowser = null;
+    }
+  });
+
+  test("No overwrite", function()
+  {
+    let unhook = hook(gBrowser, "foo", function()
+    {
+      results.push(-1);
+    });
+
+    gBrowser.foo(0);
+    deepEqual(results, [-1, 0], "Registered our hook");
+
+    results = [];
+    unhook();
+    gBrowser.foo(0);
+    deepEqual(results, [0], "Unregistered our hook");
+  });
+
+  test("Well-implemented overwrite", function()
+  {
+    let unhook = hook(gBrowser, "foo", function()
+    {
+      results.push(-1);
+    });
+
+    let orig = gBrowser.foo;
+    gBrowser.foo = function()
+    {
+      results.push(1);
+      orig.apply(this, arguments);
+    };
+
+    gBrowser.foo(0);
+    deepEqual(results, [1, -1, 0], "Registered our hook and third-party hook");
+
+    results = [];
+    gBrowser.foo = orig;
+    gBrowser.foo(0);
+    deepEqual(results, [-1, 0], "Unregistered third-party hook");
+
+    results = [];
+    unhook();
+    gBrowser.foo(0);
+    deepEqual(results, [0], "Unregistered our hook");
+  });
+
+  test("Poorly implemented overwrite", function()
+  {
+    let unhook = hook(gBrowser, "foo", function()
+    {
+      results.push(-1);
+    });
+
+    let func = "results.push(1);";
+    eval("gBrowser.foo = " + gBrowser.foo.toString().replace("{", "{" + func));
+
+    gBrowser.foo(0);
+    deepEqual(results, [-1, 1, 0], "Registered our hook and third-party hook");
+
+    results = [];
+    eval("gBrowser.foo = "+gBrowser.foo.toString().replace(func, ""));
+    gBrowser.foo(0);
+    deepEqual(results, [-1, 0], "Unregistered third-party hook");
+
+    results = [];
+    unhook();
+    gBrowser.foo(0);
+    deepEqual(results, [0], "Unregistered our hook");
+  });
+
+  test("Best implemented overwrite", function()
+  {
+    let unhook = hook(gBrowser, "foo", function()
+    {
+      results.push(-1);
+    });
+
+    let unhook2 = hook(gBrowser, "foo", function()
+    {
+      results.push(1);
+    });
+    gBrowser.foo(0);
+    deepEqual(results, [1, -1, 0], "Registered our hook and third-party hook");
+
+    results = [];
+    unhook2();
+    gBrowser.foo(0);
+    deepEqual(results, [-1, 0], "Unregistered third-party hook");
+
+    results = [];
+    unhook();
+    gBrowser.foo(0);
+    deepEqual(results, [0], "Unregistered our hook");
+  });
+
+})();