Reset the default value of touch event flag back to "Auto".

content/browser/renderer_host/render_view_host_impl.cc

 // 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.
 
 #include "content/browser/renderer_host/render_view_host_impl.h"
 
 #include <set>
 #include <string>
 #include <utility>
 #include <vector>
@@ skipping 424 matching lines @@
   // is disabled with a command-line switch or the equivalent field trial is
   // is set to "Enabled".
   prefs.user_gesture_required_for_media_playback = !command_line.HasSwitch(
       switches::kDisableGestureRequirementForMediaPlayback);
 
   prefs.progress_bar_completion = GetProgressBarCompletionPolicy();
 
   prefs.use_solid_color_scrollbars = true;
 #endif
 
-  prefs.touch_event_api_enabled =
-      !command_line.HasSwitch(switches::kTouchEvents) ||
-      command_line.GetSwitchValueASCII(switches::kTouchEvents) !=
-          switches::kTouchEventsDisabled;
   prefs.device_supports_touch = ui::GetTouchScreensAvailability() ==
                                 ui::TouchScreensAvailability::ENABLED;
+  const std::string touch_enabled_switch =
+      command_line.HasSwitch(switches::kTouchEvents)
+          ? command_line.GetSwitchValueASCII(switches::kTouchEvents)
+          : switches::kTouchEventsAuto;
+  prefs.touch_event_api_enabled =
+      (touch_enabled_switch == switches::kTouchEventsAuto)
+          ? prefs.device_supports_touch
+          : (touch_enabled_switch.empty() ||
+             touch_enabled_switch == switches::kTouchEventsEnabled);
   std::tie(prefs.available_pointer_types, prefs.available_hover_types) =
       ui::GetAvailablePointerAndHoverTypes();
   prefs.primary_pointer_type =
       ui::GetPrimaryPointerType(prefs.available_pointer_types);
   prefs.primary_hover_type =
       ui::GetPrimaryHoverType(prefs.available_hover_types);
 
 #if defined(OS_ANDROID)
   prefs.device_supports_mouse = false;
 #endif
@@ skipping 614 matching lines @@
   } else {
     render_view_ready_on_process_launch_ = true;
   }
 }
 
 void RenderViewHostImpl::RenderViewReady() {
   delegate_->RenderViewReady(this);
 }
 
 }  // namespace content