Make chrome GN build work in component mode.

content/public/renderer/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/features.gni")
 import("//content/renderer/renderer.gni")
 
-source_set("renderer") {
+# See //content/BUILD.gn for how this works.
+group("renderer") {
+  if (is_component_build) {
+    deps = [ "//content" ]
+  } else {
+    deps = [ ":renderer_sources" ]
+  }
+  forward_dependent_configs_from = deps
+}
+
+source_set("renderer_sources") {
+  visibility = [ "//content/*" ]
+
   sources = rebase_path(content_renderer_gypi_values.public_renderer_sources,
                         ".", "//content")
 
   configs += [
     "//content:content_implementation",
   ]
 
   deps = [
-    "//content/public/common",
+    "//content/public/common:common_sources",
     "//content/renderer",
     "//skia",
     "//third_party/libjingle",
     "//third_party/WebKit/public:blink_headers",
     "//third_party/widevine/cdm:version_h",
     "//ui/gfx",
     "//v8",
   ]
 
   allow_circular_includes_from = [
     # This target is a pair with content/renderer. They always go together and
     # include headers from each other.
-    "//content/renderer",
+    # TODO(brettw) enable this when this permits non-dependent targets.
+    #"//content/renderer",
   ]
 
   if (enable_webrtc) {
     sources += rebase_path(
         content_renderer_gypi_values.public_renderer_webrtc_sources,
         ".", "//content")
   }
 }