Add browser_tests to the GN build.

Other misc fixes including:

Add "data_deps" to the templates in BUILDCONFIG. This was renamed from "datadeps" a while ago but both are still supported.

extension_management_test_util.cc includes a generated file policy_constants. GYP generates this with an extra "policy" directory but GN doesn't. The way GYP has the dirs set up, though, using only one "policy" works (and this is what other files do) so I just changed the include.

TBR=dpranke

Review URL: https://codereview.chromium.org/824373003

Cr-Commit-Position: refs/heads/master@{#310276}
diff --git a/chrome/browser/extensions/extension_management_test_util.cc b/chrome/browser/extensions/extension_management_test_util.cc
index 1876316..618eb0bd 100644
--- a/chrome/browser/extensions/extension_management_test_util.cc
+++ b/chrome/browser/extensions/extension_management_test_util.cc
@@ -13,7 +13,7 @@
 #include "components/policy/core/common/policy_map.h"
 #include "components/policy/core/common/policy_namespace.h"
 #include "components/policy/core/common/policy_types.h"
-#include "policy/policy/policy_constants.h"
+#include "policy/policy_constants.h"
 
 namespace extensions {