Adding metrics logging for Simplified Gesture Navigation.

content/browser/web_contents/aura/gesture_nav_simple.h

 // Copyright 2014 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 CONTENT_BROWSER_WEB_CONTENTS_AURA_GESTURE_NAV_SIMPLE_H_
 #define CONTENT_BROWSER_WEB_CONTENTS_AURA_GESTURE_NAV_SIMPLE_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "content/browser/renderer_host/overscroll_controller_delegate.h"
+#include "content/browser/web_contents/aura/types.h"
 
 namespace content {
 
 class Affordance;
 class WebContentsImpl;
 
 // A simple delegate for the overscroll controller that paints an arrow on top
 // of the web-contents as a hint for pending navigations from overscroll.
 class GestureNavSimple : public OverscrollControllerDelegate {
  public:
@@ skipping 14 matching lines @@
   bool OnOverscrollUpdate(float delta_x, float delta_y) override;
   void OnOverscrollComplete(OverscrollMode overscroll_mode) override;
   void OnOverscrollModeChange(OverscrollMode old_mode,
                               OverscrollMode new_mode,
                               OverscrollSource source) override;
   base::Optional<float> GetMaxOverscrollDelta() const override;
 
   WebContentsImpl* web_contents_;
   std::unique_ptr<Affordance> affordance_;
   float completion_threshold_;
+  NavigationDirection direction_ = NavigationDirection::NONE;

[mohsen, 2017/07/20 18:00:41]

Instead of adding |direction_|, can you use OverscrollMode to derive direction
whenever necessary? (Similar to what ShouldNavigateForward/Back() does). E.g.:

  bool IsForwardNavigation(OverscrollMode mode) {
    return mode == (base::i18n::IsRTL() ? OVERSCROLL_EAST : OVERSCROLL_WEST);
  }

  bool IsBackNavigation(OverscrollMode mode) { ... }

These can be used in ShouldNavigateForward/Back() as well.

[mfomitchev, 2017/07/21 00:10:07]

Got rid of direction. I left NavigationDirection, since it's I think it's a bit
more explicit than bools, plus it's used in the old gesture nav.

+  OverscrollSource source_ = OverscrollSource::NONE;
 
   DISALLOW_COPY_AND_ASSIGN(GestureNavSimple);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_WEB_CONTENTS_AURA_GESTURE_NAV_SIMPLE_H_