Add content renderer to the GN build

content/renderer/renderer.gni

Index: content/renderer/renderer.gni
diff --git a/content/common/common.gni b/content/renderer/renderer.gni
similarity index 55%
copy from content/common/common.gni
copy to content/renderer/renderer.gni
index 36cb33960fac6f270199644609c7999b8f9f0a28..2b638894a28d29bd932b040891816e1de0876347 100644
--- a/content/common/common.gni
+++ b/content/renderer/renderer.gni
@@ -2,13 +2,13 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-# This file defines the content common gypi values. This file is read once and
-# cached, which is a performance optimization that allows us to share the
+# This file defines the content renderer gypi values. This file is read once
+# and cached, which is a performance optimization that allows us to share the
 # results of parsing the .gypi file between the public and private BUILD.gn
 # files. It also saves us from duplicating this exec_script call.
-content_common_gypi_values = exec_script(
+content_renderer_gypi_values = exec_script(
     "//build/gypi_to_gn.py",
-    [ rebase_path("../content_common.gypi") ],
+    [ rebase_path("../content_renderer.gypi") ],
     "scope",
-    [ "../content_common.gypi" ])
+    [ "../content_renderer.gypi" ])