Merge to XFA: Add pdfium_unittests to BUILD.gn

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 0d3d6938da457d1bf6d4c17e149c081f7c0e7249..c4e4580469e41750d2054bcb0100ebcf320c4f78 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1540,3 +1540,19 @@ static_library("xfa") {
     "//v8:v8_libplatform",
   ]
 }
+
+test("pdfium_unittests") {
+  sources = [
+    "core/src/fxcrt/fx_basic_bstring_unittest.cpp",
+    "testing/fx_string_testhelpers.cpp",
+    "testing/fx_string_testhelpers.h",
+  ]
+  deps = [
+    "//testing/gtest",
+    "//testing/gtest:gtest_main",
+    ":pdfium"
+  ]
+  include_dirs = [ "." ]
+  configs -= [ "//build/config/compiler:chromium_code" ]
+  configs += [ ":pdfium_config", "//build/config/compiler:no_chromium_code" ]
+}