Revert of [Sync] Eliminate verifier profile from sync_integration_tests

chrome/browser/sync/test/integration/extensions_helper.cc

Index: chrome/browser/sync/test/integration/extensions_helper.cc
diff --git a/chrome/browser/sync/test/integration/extensions_helper.cc b/chrome/browser/sync/test/integration/extensions_helper.cc
index 1dad8f42181b51ea6efebe6800e145ff705d3a29..7f9a2fbe99c6c43940336ef35077dd3b10ec597a 100644
--- a/chrome/browser/sync/test/integration/extensions_helper.cc
+++ b/chrome/browser/sync/test/integration/extensions_helper.cc
@@ -70,11 +70,9 @@
 }
 
 std::string InstallExtensionForAllProfiles(int index) {
-  std::string extension_id;
-  for (auto* profile : test()->GetAllProfiles()) {
-    extension_id = InstallExtension(profile, index);
-  }
-  return extension_id;
+  for (int i = 0; i < test()->num_clients(); ++i)
+    InstallExtension(test()->GetProfile(i), index);
+  return InstallExtension(test()->verifier(), index);
 }
 
 void UninstallExtension(Profile* profile, int index) {