Allow for pausing background tabs on desktop via about:flags.

chrome/common/pause_tabs_field_trial.h

Index: chrome/common/pause_tabs_field_trial.h
diff --git a/chrome/common/pause_tabs_field_trial.h b/chrome/common/pause_tabs_field_trial.h
new file mode 100644
index 0000000000000000000000000000000000000000..bbc8f69d828661c610205f916c56ddaefb92308f
--- /dev/null
+++ b/chrome/common/pause_tabs_field_trial.h
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+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_COMMON_PAUSE_TABS_FIELD_TRIAL_H_
+#define CHROME_COMMON_PAUSE_TABS_FIELD_TRIAL_H_
+
+#include "base/feature_list.h"
+
+namespace pausetabs {
+
+const base::Feature kFeature{"PauseBackgroundTabs",
+                             base::FEATURE_DISABLED_BY_DEFAULT};
+
+const char kFeatureName[] = "pause-background-tabs";
+
+// Mode values.
+const char kModeParamMinimal[] = "minimal";
+const char kModeParamLow[] = "low";
+const char kModeParamMedium[] = "medium";
+const char kModeParamHigh[] = "high";
+const char kModeParamMax[] = "max";
+
+}  // namespace pausetabs
+
+#endif  // CHROME_COMMON_PAUSE_TABS_FIELD_TRIAL_H_