Move some component's GN build files to main tree.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 73d5ef9a84b1571e46bf74eec6f49b01a0dd2c9c..dc3ead4e1e6150ad919ad6cde9ffccda8e3df6c2 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -18,10 +18,10 @@ group("root") {
     #"//base(//build/toolchain/nacl:x86_newlib)",
 
     #"//chrome",
-    #"//components/language_usage_metrics",
-    #"//components/navigation_metrics",
-    #"//components/onc:onc_component",
-    #"//components/startup_metric_utils",
+    "//components/language_usage_metrics",
+    "//components/navigation_metrics",
+    "//components/onc",
+    "//components/startup_metric_utils",
     #"//components/translate:translate_core_browser",
     #"//components/translate:translate_core_common",
     #"//crypto",
@@ -38,6 +38,6 @@ group("root") {
     #"//third_party/zlib",
     #"//skia",
     "//tools/gn",
-    #"//url",
+    "//url",
   ]
 }