Add the BUILD files for content_resources.

content/app/resources/BUILD.gn

Index: content/app/resources/BUILD.gn
diff --git a/extensions/shell/BUILD.gn b/content/app/resources/BUILD.gn
similarity index 61%
copy from extensions/shell/BUILD.gn
copy to content/app/resources/BUILD.gn
index 5e501e3c1bf4ccaec27017fb01fd32e9ff23bc92..967f919da883c0de4defde5caeaeeb3c7e499f44 100644
--- a/extensions/shell/BUILD.gn
+++ b/content/app/resources/BUILD.gn
@@ -5,9 +5,10 @@
 import("//tools/grit/grit_rule.gni")
 
 grit("resources") {
-  source = "app_shell_resources.grd"
+  source = "content_resources.grd"

[Nico, 2014/08/20 15:41:10]

Why does this rule exist both here and in content/BUILD.gn ?

   outputs = [
-    "grit/app_shell_resources.h",
-    "app_shell_resources.pak",
+    "grit/content_resources.h",
+    "content_resources_100_percent.pak",
+    "content_resources_200_percent.pak",
   ]
 }