Set the unique_event_id when converting from TouchEvent to WebTouchEvent

ui/events/gestures/motion_event_aura_unittest.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.
 
 // MSVC++ requires this to be set before any other includes to get M_PI.
 #define _USE_MATH_DEFINES
 
 #include <cmath>
 
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 472 matching lines @@
   MotionEventAura event;
   EXPECT_TRUE(event.OnTouch(TouchWithType(ET_TOUCH_PRESSED, id)));
   TouchEvent move0 = TouchWithPosition(ET_TOUCH_PRESSED, id, 10, 20, 10, 20);
   EXPECT_TRUE(event.OnTouch(move0));
 
   TouchEvent move1 = TouchWithPosition(ET_TOUCH_MOVED, id, 11, 21, 11, 21);
   EXPECT_TRUE(event.OnTouch(move1));
   EXPECT_FALSE(event.OnTouch(move1));
 }
 
+// Test after converting touch events into motion events, motion events should
+// have the same unique_event_id as touch events.
+TEST(MotionEventAuraTest, UniqueEventID) {
+  MotionEventAura event;
+
+  TouchEvent press0 = TouchWithType(ET_TOUCH_PRESSED, 3);
+  EXPECT_TRUE(event.OnTouch(press0));
+  EXPECT_EQ(MotionEvent::ACTION_DOWN, event.GetAction());
+  ASSERT_EQ(1U, event.GetPointerCount());
+  EXPECT_EQ(event.GetUniqueEventId(), press0.unique_event_id());
+
+  TouchEvent press1 = TouchWithType(ET_TOUCH_PRESSED, 6);
+  EXPECT_TRUE(event.OnTouch(press1));
+  EXPECT_EQ(MotionEvent::ACTION_POINTER_DOWN, event.GetAction());
+  EXPECT_EQ(2U, event.GetPointerCount());
+  EXPECT_EQ(event.GetUniqueEventId(), press1.unique_event_id());
+}
+
 }  // namespace ui