Add policy_templates target for GN.

BUG=462362

Review URL: https://codereview.chromium.org/957283003

Cr-Commit-Position: refs/heads/master@{#319616}

components/policy/BUILD.gn

@@ -117,6 +117,26 @@ if (enable_configuration_policy) {
     ]
   }
 
+  grit("policy_templates") {
+    import("resources/policy_templates.gni")
+    source = "resources/policy_templates.grd"
+    use_qualified_include = true
+    output_dir = "$root_gen_dir/chrome"
+    outputs = policy_templates_doc_outputs
+    if (is_android) {
+      outputs += policy_templates_android_outputs
+    }
+    if (is_linux) {
+      outputs += policy_templates_linux_outputs
+    }
+    if (is_mac) {
+      outputs += policy_templates_mac_outputs
+    }
+    if (is_win) {
+      outputs += policy_templates_windows_outputs
+    }
+  }
+
   proto_library("cloud_policy_proto_generated_compile") {
     sources = [
       cloud_policy_proto_path,
@@ -218,4 +238,4 @@ if (enable_configuration_policy) {
     ]
   }
 }
-#TODO(GYP) policy templates, chrome_manifest_bundle
+#TODO(GYP) chrome_manifest_bundle