Add browser_extensions to GN build.

BUG=
R=jamesr@chromium.org

Review URL: https://codereview.chromium.org/383083010

git-svn-id: http://src.chromium.org/svn/trunk/src/build@283052 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

config/features.gni

@@ -156,3 +156,6 @@ enable_one_click_signin = is_win || is_mac || (is_linux && !is_chromeos)
 # Chrome OS: whether to also build the upcoming version of
 # ChromeVox, which can then be enabled via a command-line switch.
 enable_chromevox_next = false
+
+# Use brlapi from brltty for braille display support.
+use_brlapi = is_chromeos

config/linux/BUILD.gn

@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 import("//build/config/linux/pkg_config.gni")
+import("//build/config/features.gni")
 import("//build/config/sysroot.gni")
 import("//build/config/ui.gni")
 import("//tools/generate_library_loader/generate_library_loader.gni")
@@ -116,6 +117,22 @@ pkg_config("gconf") {
   defines = [ "USE_GCONF" ]
 }
 
+# If brlapi isn't needed, don't require it to be installed.
+if (use_brlapi) {
+  config("brlapi_config") {
+    defines = [ "USE_BRLAPI" ]
+  }
+
+  # TODO(GYP) linux_link_brlapi support. Is this needed?
+  generate_library_loader("libbrlapi") {
+    name = "LibBrlapiLoader"
+    output_h = "libbrlapi.h"
+    output_cc = "libbrlapi_loader.cc"
+    header = "<brlapi.h>"
+    config = ":brlapi_config"
+  }
+}
+
 pkg_config("gio_config") {
   packages = [ "gio-2.0" ]
   defines = [ "USE_GIO" ]