Add more components_unittests to GN build

components/translate/core/language_detection/BUILD.gn

Index: components/translate/core/language_detection/BUILD.gn
diff --git a/components/translate/core/language_detection/BUILD.gn b/components/translate/core/language_detection/BUILD.gn
index 57e1d10fb642fb951b19125a5339e7234c8395c9..a1d15efe0fb982cbe33d0856d98c6740a8aa01c1 100644
--- a/components/translate/core/language_detection/BUILD.gn
+++ b/components/translate/core/language_detection/BUILD.gn
@@ -4,7 +4,7 @@
 
 import("//build/config/features.gni")
 
-static_library("language_detection") {
+source_set("language_detection") {
   sources = [
     "language_detection_util.cc",
     "language_detection_util.h",
@@ -18,8 +18,20 @@ static_library("language_detection") {
 
   if (cld_version == 1) {
     deps += [ "//third_party/cld" ]
+  } else if (cld_version == 2) {
+    deps += [ "//third_party/cld_2:cld2_platform_impl" ]
+  } else {
+    assert(false, "Need a CLD version")
   }
-  if (cld_version == 2) {
-    deps += [ "//third_party/cld_2" ]
-  }
+}
+
+source_set("unit_tests") {
+  testonly = true
+  sources = [
+    "language_detection_util_unittest.cc",
+  ]
+  deps = [
+    ":language_detection",
+    "//testing/gtest",
+  ]
 }