Support double-tap to click in touch accessibility controller.

chrome/browser/chromeos/accessibility/touch_exploration_controller_browsertest.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 "ui/chromeos/touch_exploration_controller.h"
 
 #include "ash/accessibility_delegate.h"
 #include "ash/shell.h"
 #include "ash/test/ash_test_base.h"
 #include "chrome/test/base/in_process_browser_test.h"
@@ skipping 37 matching lines @@
 // get rewritten when the touch exploration mode is on, and aren't affected
 // after the touch exploration mode is turned off.
 IN_PROC_BROWSER_TEST_F(TouchExplorationTest, ToggleOnOff) {
   aura::Window* root_window = ash::Shell::GetInstance()->GetPrimaryRootWindow();
   scoped_ptr<ui::test::TestEventHandler>
       event_handler(new ui::test::TestEventHandler());
   root_window->AddPreTargetHandler(event_handler.get());
   SwitchTouchExplorationMode(true);
   aura::test::EventGenerator generator(root_window);
 
+  generator.set_current_location(gfx::Point(100, 200));
   generator.PressTouchId(1);
+  // Since the touch exploration controller doesn't know if the user is
+  // double-tapping or not, touch exploration is only initiated if the
+  // user moves more than 8 pixels away from the initial location (the "slop"),
+  // or after 300 ms has elapsed.
+  generator.MoveTouchId(gfx::Point(109, 209), 1);
   // Number of mouse events may be greater than 1 because of ET_MOUSE_ENTERED.
   EXPECT_GT(event_handler->num_mouse_events(), 0);
   EXPECT_EQ(0, event_handler->num_touch_events());
   event_handler->Reset();
 
   SwitchTouchExplorationMode(false);
   generator.MoveTouchId(gfx::Point(11, 12), 1);
   EXPECT_EQ(0, event_handler->num_mouse_events());
   EXPECT_EQ(1, event_handler->num_touch_events());
   event_handler->Reset();
 
   SwitchTouchExplorationMode(true);
+  generator.set_current_location(gfx::Point(500, 600));
   generator.PressTouchId(2);
+  generator.MoveTouchId(gfx::Point(509, 609), 2);
   EXPECT_GT(event_handler->num_mouse_events(), 0);
   EXPECT_EQ(0, event_handler->num_touch_events());
 
   SwitchTouchExplorationMode(false);
   root_window->RemovePreTargetHandler(event_handler.get());
 }
 
 }  // namespace ui