Add browser_extensions to GN build.

chrome/common/BUILD.gn

Index: chrome/common/BUILD.gn
diff --git a/chrome/common/BUILD.gn b/chrome/common/BUILD.gn
index 49e7552b3e9274b992ac7c0d2dfc877afbf27c77..c2ffc591ce903a576674d1324e2043554f20aa8a 100644
--- a/chrome/common/BUILD.gn
+++ b/chrome/common/BUILD.gn
@@ -70,6 +70,7 @@ static_library("common") {
       "//components/autofill/content/common",
       "//components/autofill/core/common",
       "//components/translate/content/common",
+      "//extensions/common/api",
       "//ipc",
       "//third_party/adobe/flash:flapper_version_h",
       "//third_party/re2",
@@ -77,7 +78,6 @@ static_library("common") {
       #'<(DEPTH)/components/components.gyp:password_manager_core_common',  TODO(GYP)
       #'<(DEPTH)/components/components.gyp:signin_core_common',  TODO(GYP)
       #'<(DEPTH)/components/nacl.gyp:nacl_common',  TODO(GYP)
-      #'<(DEPTH)/extensions/common/api/api.gyp:extensions_api',  TODO(GYP)
       #'<(DEPTH)/extensions/extensions.gyp:extensions_common',  TODO(GYP)
     ]
   }