Add User Actions and adding more details to UMA metrics for overscroll navigation

content/browser/web_contents/aura/uma_navigation_type.h

Index: content/browser/web_contents/aura/uma_navigation_type.h
diff --git a/content/browser/web_contents/aura/uma_navigation_type.h b/content/browser/web_contents/aura/uma_navigation_type.h
new file mode 100644
index 0000000000000000000000000000000000000000..53294b9d9196368d311d334630d2ac2a872c6b81
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+++ b/content/browser/web_contents/aura/uma_navigation_type.h
@@ -0,0 +1,18 @@
+// Copyright 2017 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.
+
+namespace content {
+
+// Note that this enum is used to back an UMA histogram, so it should be
+// treated as append-only.
+enum UmaNavigationType {
+  NAVIGATION_TYPE_NONE,
+  FORWARD_TOUCHPAD,
+  BACK_TOUCHPAD,
+  FORWARD_TOUCHSCREEN,
+  BACK_TOUCHSCREEN,
+  NAVIGATION_TYPE_COUNT,
+};
+
+}  // namespace content