Postpone rail application for touch scrolling - chrome side.

ui/events/gesture_detection/gesture_detection_switches.cc

+// Copyright 2015 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 "ui/events/gesture_detection/gesture_detection_switches.h"
+
+#include "base/command_line.h"
+#include "base/logging.h"
+
+namespace switches {
+
+// Postpone the application of scroll rails until after gesture
+// recognition. This will result in views logic seeing unrailed
+// scrolls. See crbug.com/469789 for details, and crbug.com/472223 for
+// the bug to remove this flag.
+const char kScrollRailsPostponed[] = "scroll-rails-postponed";
+const char kScrollRailsPostponedAuto[] = "auto";
+const char kScrollRailsPostponedEnabled[] = "enabled";
+const char kScrollRailsPostponedDisabled[] = "disabled";
+
+}  // namespace switches
+
+namespace ui {
+
+bool PostponeRailApplication() {
+  const base::CommandLine& command_line =
+      *base::CommandLine::ForCurrentProcess();
+  const std::string scroll_rails_postponed_switch =
+      command_line.HasSwitch(switches::kScrollRailsPostponed) ?
+      command_line.GetSwitchValueASCII(switches::kScrollRailsPostponed) :
+      switches::kScrollRailsPostponedAuto;
+  bool default_value = true;
+
+  if (scroll_rails_postponed_switch == switches::kScrollRailsPostponedEnabled)
+    return true;
+  if (scroll_rails_postponed_switch == switches::kScrollRailsPostponedDisabled)
+    return false;
+  if (scroll_rails_postponed_switch == switches::kScrollRailsPostponedAuto)
+    return default_value;
+  LOG(ERROR) << "Invalid --scroll-rails-postponed option: "
+             << scroll_rails_postponed_switch;
+  return default_value;
+}
+
+}  // namespace ui