Add components/keyed_service to GN build.

components/keyed_service.gypi

Index: components/keyed_service.gypi
diff --git a/components/keyed_service.gypi b/components/keyed_service.gypi
index b03a204f9fffb6f99311d62dcbee5df169caf8e2..2f0ceefb6a0b80b0ff5e9aa23ebc1d140732e3cb 100644
--- a/components/keyed_service.gypi
+++ b/components/keyed_service.gypi
@@ -5,6 +5,7 @@
 {
   'targets': [
     {
+      # GN version: //components/keyed_service/core:core

[blundell, 2014/06/19 20:19:01]

What does this syntax mean, out of curiosity?

[brettw, 2014/06/19 20:21:22]

The "core" target in the "components/keyed_service/core" directory. If you leave
off the colon, it will duplicate the directory name for the target name, so this
label is the same with and without the ":core". The double-slash means "source
root".

       'target_name': 'keyed_service_core',
       'type': '<(component)',
       'defines': [
@@ -32,6 +33,7 @@
     ['OS != "ios"', {
       'targets': [
         {
+          # GN version: //components/keyed_service/content:content
           'target_name': 'keyed_service_content',
           'type': '<(component)',
           'defines': [