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

content/browser/web_contents/aura/gesture_nav_simple.cc

 // 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.
 
 #include "content/browser/web_contents/aura/gesture_nav_simple.h"
 
 #include <utility>
 
 #include "base/macros.h"
 #include "cc/paint/paint_flags.h"
@@ skipping 356 matching lines @@
   CompleteGestureAnimation();
 
   NavigationControllerImpl& controller = web_contents_->GetController();
   if (ShouldNavigateForward(controller, overscroll_mode))
     controller.GoForward();
   else if (ShouldNavigateBack(controller, overscroll_mode))
     controller.GoBack();
 }
 
 void GestureNavSimple::OnOverscrollModeChange(OverscrollMode old_mode,
-                                              OverscrollMode new_mode) {
+                                              OverscrollMode new_mode,
+                                              OverscrollSource source) {
   NavigationControllerImpl& controller = web_contents_->GetController();
   if (!ShouldNavigateForward(controller, new_mode) &&
       !ShouldNavigateBack(controller, new_mode)) {
     AbortGestureAnimation();
     return;
   }
 
   aura::Window* window = web_contents_->GetNativeView();
   const gfx::Rect& window_bounds = window->bounds();
+  DCHECK_NE(source, OverscrollSource::NONE);
+  float start_threshold =
+      source == OverscrollSource::TOUCHPAD
+          ? GetOverscrollConfig(
+                OVERSCROLL_CONFIG_HORIZ_THRESHOLD_START_TOUCHPAD)
+          : GetOverscrollConfig(
+                OVERSCROLL_CONFIG_HORIZ_THRESHOLD_START_TOUCHSCREEN);

[mohsen, 2017/02/23 19:19:10]

nit: I would put conditional ternary operator inside GetOverscrollConfig() to
avoid typing GetOverscrollConfig() twice!

   completion_threshold_ =
       window_bounds.width() *
           GetOverscrollConfig(OVERSCROLL_CONFIG_HORIZ_THRESHOLD_COMPLETE) -
-      GetOverscrollConfig(OVERSCROLL_CONFIG_HORIZ_THRESHOLD_START_TOUCHSCREEN);
+      start_threshold;
 
   affordance_.reset(new Affordance(new_mode, window_bounds));
 
   // Adding the affordance as a child of the content window is not sufficient,
   // because it is possible for a new layer to be parented on top of the
   // affordance layer (e.g. when the navigated-to page is displayed while the
   // completion animation is in progress). So instead, it is installed on top of
   // the content window as its sibling. Note that the affordance itself makes
   // sure that its contents are clipped to the bounds given to it.
   ui::Layer* parent = window->layer()->parent();
   parent->Add(affordance_->root_layer());
   parent->StackAtTop(affordance_->root_layer());
 }
 
 }  // namespace content