Android: Do not build files not needed on the platform.

chrome/browser/BUILD.gn

Index: chrome/browser/BUILD.gn
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index f66bb8be89970259f4a8f82b4d2c2aba6a77d207..1219a477e357148536c472316ea7d8af6e097250 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -1104,6 +1104,15 @@ source_set("test_support") {
     ]
   }
 
+  if (is_android) {
+    sources -= [
+      "sessions/session_service_test_helper.cc",
+      "sessions/session_service_test_helper.h",
+      "ui/webui/signin/login_ui_test_utils.cc",
+      "ui/webui/signin/login_ui_test_utils.h",
+    ]
+  }
+
   if (enable_extensions) {
     sources += [
       "extensions/extension_action_test_util.cc",