Implement API features for the Extension API feature system

chrome/test/data/extensions/extension_api_unittest/api_features.json

+{
+  "test1": {
+    "extension_types": ["extension"],
+    "contexts": ["content_script"]
+  },
+  "test2": {
+    "extension_types": ["extension"],
+    "contexts": ["blessed_extension"]
+  },
+  "test3": {
+    "extension_types": ["extension"],
+    "contexts": ["content_script", "blessed_extension"]
+  },
+  "test4": {
+    "extension_types": ["extension"],
+    "contexts": ["blessed_extension"]
+  },
+  "test4.foo": {
+    "extension_types": ["extension"],
+    "contexts": ["content_script", "blessed_extension"]
+  },

[not at google - send to devlin, 2013/03/26 00:34:48]

it would also be good to test just ['content_scripts'] here too.

[cduvall, 2013/03/26 19:24:05]

Done.

+  "test4.bar": {
+    "extension_types": ["extension"],
+    "dependencies": ["api:test4.foo"]
+  },
+  "test5": {
+    "extension_types": ["extension"],
+    "contexts": ["blessed_extension"]
+  },
+  "test5.foo": {
+    "extension_types": ["extension"],
+    "dependencies": ["test2:monkey"]
+  },
+  "test5.bar": {
+    "extension_types": ["extension"],
+    "dependencies": ["api:test5.foo"]
+  }

[not at google - send to devlin, 2013/03/26 00:34:48]

some more tests:
- matches
- how it interacts with web_page context
- deeper nesting
- a content_script-only API namespace with blessed children.

[cduvall, 2013/03/26 19:24:05]

Done.

+}