Adding metrics logging for Simplified Gesture Navigation.

content/browser/web_contents/aura/gesture_nav_simple.h

Index: content/browser/web_contents/aura/gesture_nav_simple.h
diff --git a/content/browser/web_contents/aura/gesture_nav_simple.h b/content/browser/web_contents/aura/gesture_nav_simple.h
index 70b474f3f1fc2bab9512ec5213485cc0871bedea..00d09e5bbcd843bf7fb75827540be1372e51cf55 100644
--- a/content/browser/web_contents/aura/gesture_nav_simple.h
+++ b/content/browser/web_contents/aura/gesture_nav_simple.h
@@ -9,6 +9,7 @@
 
 #include "base/macros.h"
 #include "content/browser/renderer_host/overscroll_controller_delegate.h"
+#include "content/browser/web_contents/aura/types.h"
 
 namespace content {
 
@@ -43,6 +44,8 @@ class GestureNavSimple : public OverscrollControllerDelegate {
   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);
 };