Revert of Remove configuration policy from chrome build files.

chrome/browser/extensions/BUILD.gn

Index: chrome/browser/extensions/BUILD.gn
diff --git a/chrome/browser/extensions/BUILD.gn b/chrome/browser/extensions/BUILD.gn
index 35aeeaa9639f780f5cd75a1e0ba8044afa7c1212..a5124180e620064d4873d990ecc3e36dc3a9826f 100644
--- a/chrome/browser/extensions/BUILD.gn
+++ b/chrome/browser/extensions/BUILD.gn
@@ -47,7 +47,6 @@
     "//components/data_reduction_proxy/proto:data_reduction_proxy_proto",
     "//components/dom_distiller/core",
     "//components/onc",
-    "//components/policy",
     "//components/proximity_auth",
     "//components/resources",
     "//components/strings",
@@ -163,6 +162,17 @@
     }
   }
 
+  if (enable_configuration_policy) {
+    deps += [ "//components/policy" ]
+    sources += [
+      "policy_handlers.cc",
+      "policy_handlers.h",
+    ]
+    sources += rebase_path(gypi_values.chrome_browser_extensions_policy_sources,
+                           ".",
+                           "//chrome")
+  }
+
   if (enable_webrtc) {
     sources += [ "api/webrtc_logging_private/webrtc_logging_private_api.cc" ]
   } else {