Show hosted app requests to extensions

chrome/test/data/extensions/api_test/webrequest_hosted_app/manifest.json

 {
-    "name": "WebRequest + incognito = crash",
-    "incognito":"split",
+    "name": "webRequest extension",
     "version": "1",

[not at google - send to devlin, 2015/09/08 16:09:20]

I'm a little confused, the comments in the C++ test + this directory name + plus
what this extension actually does, it seems to be both a hosted app and an
extension.

Ideally we'd have 2 extensions,
1. a generic one which blocks requests and does a chrome.test.sendMessage each
time. configured with a URL path I guess. maybe it would start up, ask the
browser what paths to block, then start blocking requests.
2. a really simple hosted app that tries to do a fetch (or whatever) - your
index.html here.

or, some other variation which is more clear to me who is supposed to do what.

[robwu, 2015/09/08 17:19:48]

The directory containing the tests is named after the test
(ExtensionWebRequestApiTest.HostedAppRequest).

These files (manifest.json, background.js) are a dead-simple extension that
reports the webRequest event to the test runner.
The hosted app itself consists of two parts:
1. index.html (also in this directory).
2. The manifest file, generated on the fly in the test runner because the URL of
the hosted app varies at every test run because of the dynamic port.

The code of the actual test (in C++) closely matches the desired test logic (see
below) (with little boilerplate, except for the set up of the hosted app
manifest):
1. Load the (generated) hosted app.
2. Load the webRequest extension.
3. Navigate to the URL of the app.
4. Wait until the extension reports the events for both the navigation and the
fetch request and complete the test.

Just testing the navigation is sufficient for the bug, but I also added the
fetch check in case it becomes relevant in the future.

     "manifest_version": 2,
     "background": {
-        "scripts": ["background.js"]
+        "scripts": ["background.js"],
+        "persistent": true
     },
     "permissions": [
         "webRequest",
         "<all_urls>"
     ]
 }