Add missing #includes of browser_test.h.

This is a step towards doing full IWYU of browser_test.h, which will
have other benefits.

Completely mechanical and already R+ed as part of r765923.

Tbr: sky
Bug: none
Change-Id: Icb7ab728098a6cf29c0920da4b524e96a7c024c2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2186411
Commit-Queue: Peter Kasting <[email protected]>
Reviewed-by: Peter Kasting <[email protected]>
Cr-Commit-Position: refs/heads/master@{#766361}
diff --git a/chrome/browser/prefs/pref_functional_browsertest.cc b/chrome/browser/prefs/pref_functional_browsertest.cc
index 9c0624e5..c309e69 100644
--- a/chrome/browser/prefs/pref_functional_browsertest.cc
+++ b/chrome/browser/prefs/pref_functional_browsertest.cc
@@ -26,6 +26,7 @@
 #include "components/safe_browsing/core/common/safe_browsing_prefs.h"
 #include "components/sync_preferences/pref_service_syncable.h"
 #include "content/public/browser/web_contents.h"
+#include "content/public/test/browser_test.h"
 #include "content/public/test/browser_test_utils.h"
 #include "content/public/test/download_test_observer.h"
 #include "net/test/embedded_test_server/embedded_test_server.h"