Add unit tests target to GN build.

chrome/browser/BUILD.gn

Index: chrome/browser/BUILD.gn
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index 4f5629ff394e9d962eadd79f98b698359fc623df..308b028a3d90e20e7aaf69d163d0e31c2b2d0165 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -28,8 +28,24 @@ gypi_values = exec_script("//build/gypi_to_gn.py",
                           [ "../chrome_browser.gypi" ])
 
 if (is_desktop_linux) {
+  # Gnome-keyring is normally dynamically loaded. The gnome_keyring config
+  # will set this up.
   pkg_config("gnome_keyring") {
     packages = [ "gnome-keyring-1" ]
+    defines = [
+      "USE_GNOME_KEYRING",
+      "DLOPEN_GNOME_KEYRING",
+    ]
+    ignore_libs = true
+  }
+
+  # If you want to link gnome-keyring directly (use only for unit tests)
+  # ADDITIONALLY add this config on top of ":gnome_keyring". pkg-config is a
+  # bit slow, so prefer not to run it again. In practice, gnome-keyring's libs
+  # are just itself and common gnome ones we link already, so we can get away
+  # with additionally just coding the library name here.
+  config("gnome_keyring_direct") {
+    libs = [ "gnome-keyring" ]
   }
 }