Add some examples for service options in the manifest doc

This change adds examples for
can_connect_to_other_services_with_any_instance_name and
can_create_other_service_instances options, as well as capability specs.

Bug: 866967
Change-Id: Iae17a8514a1a3be44b890a4c296a57085302174d
Reviewed-on: https://chromium-review.googlesource.com/1244823
Commit-Queue: Oksana Zhuravlova <oksamyt@chromium.org>
Reviewed-by: Ken Rockot <rockot@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594813}

services/service_manager/service_manifests.md

@@ -152,7 +152,11 @@ different from the service name when connecting.
 at the same level as the browser process itself.
 
 Example:
-[content_browser](https://cs.chromium.org/chromium/src/content/public/app/mojo/content_browser_manifest.json)
+[chrome_browser](https://cs.chromium.org/chromium/src/chrome/app/chrome_manifest.json)
+
+Code in chrome_browser calls an XML parsing library function, which generates a
+random instance name to
+[isolate unrelated decode operations](https://cs.chromium.org/chromium/src/services/data_decoder/public/cpp/safe_xml_parser.cc?l=50).
 
 #### can\_create\_other\_service\_instances (bool)
 
@@ -165,6 +169,9 @@ at least at the same level as the Service Manager itself.
 Example:
 [content_browser](https://cs.chromium.org/chromium/src/content/public/app/mojo/content_browser_manifest.json)
 
+The browser manages render processes, and thus needs this privilege to manage
+the content_renderer instances on behalf of the service manager.
+
 ### interface\_provider\_specs (dictionary)
 
 The interface provider spec is a dictionary keyed by interface provider
@@ -178,6 +185,10 @@ capability spec named “service_manager:connector”. This is the
 capability spec enforced when inter-service connections are made from a
 service's `Connector` interface.
 
+Some other examples of capability specs are things like "navigation:frame",
+which enforces capability specs for interfaces retrieved through a
+frame's `InterfaceProvider`.
+
 See [README.md](README.md#service-manifests) for some examples.
 
 **Note:** Since multiple interface provider support makes the manifest files