Files app: Use push_back instead of emplace_back

Used vector::push_back() instead of vector::emplace_back() in test code,
since there is no type conversion happening here.

BUG=None
TEST=browser_tests --gtest_filter="*FilesApp*"

Change-Id: Ib8ec996d47eeed6b128b9a4bbfe9f8bb898e0790
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2210077Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: François Degros <fdegros@chromium.org>
Cr-Commit-Position: refs/heads/master@{#770504}

chrome/browser/chromeos/file_manager/file_manager_browsertest_base.cc

@@ -1536,33 +1536,32 @@ void FileManagerBrowserTestBase::SetUpCommandLine(
   std::vector<base::Feature> disabled_features;
 
   if (opts.files_ng) {
-    enabled_features.emplace_back(chromeos::features::kFilesNG);
+    enabled_features.push_back(chromeos::features::kFilesNG);
   } else {
-    disabled_features.emplace_back(chromeos::features::kFilesNG);
+    disabled_features.push_back(chromeos::features::kFilesNG);
   }
 
   if (opts.arc) {
     arc::SetArcAvailableCommandLineForTesting(command_line);
   }
+
   // Make sure to run the ARC storage UI toast tests.
-  enabled_features.emplace_back(arc::kUsbStorageUIFeature);
+  enabled_features.push_back(arc::kUsbStorageUIFeature);
 
   if (opts.documents_provider) {
-    enabled_features.emplace_back(
-        arc::kEnableDocumentsProviderInFilesAppFeature);
+    enabled_features.push_back(arc::kEnableDocumentsProviderInFilesAppFeature);
   } else {
-    disabled_features.emplace_back(
-        arc::kEnableDocumentsProviderInFilesAppFeature);
+    disabled_features.push_back(arc::kEnableDocumentsProviderInFilesAppFeature);
   }
 
   if (opts.unified_media_view) {
-    enabled_features.emplace_back(chromeos::features::kUnifiedMediaView);
+    enabled_features.push_back(chromeos::features::kUnifiedMediaView);
   } else {
-    disabled_features.emplace_back(chromeos::features::kUnifiedMediaView);
+    disabled_features.push_back(chromeos::features::kUnifiedMediaView);
   }
 
   if (opts.smbfs) {
-    enabled_features.emplace_back(features::kSmbFs);
+    enabled_features.push_back(features::kSmbFs);
   }
 
   // This is destroyed in |TearDown()|. We cannot initialize this in the