Coalesced mouse wheel event has the position of the most recent event.

content/common/input/event_with_latency_info_unittest.cc

Index: content/common/input/event_with_latency_info_unittest.cc
diff --git a/content/common/input/event_with_latency_info_unittest.cc b/content/common/input/event_with_latency_info_unittest.cc
index 45907f7117b11d39e2b7bb7b1b33b9d729671047..b7f6d5cddd6e2209a3b13f148882e7258ed764bd 100644
--- a/content/common/input/event_with_latency_info_unittest.cc
+++ b/content/common/input/event_with_latency_info_unittest.cc
@@ -313,6 +313,18 @@ TEST_F(EventWithLatencyInfoTest, WebMouseWheelEventCoalescing) {
   mouse_wheel_0.event.modifiers = WebInputEvent::ControlKey;
   mouse_wheel_1.event.modifiers = WebInputEvent::ShiftKey;
   EXPECT_FALSE(CanCoalesce(mouse_wheel_0, mouse_wheel_1));
+
+  // Coalesced event has the position of the most recent event.
+  mouse_wheel_0 = CreateMouseWheel(1, 1);
+  mouse_wheel_0.event.x = 1;
+  mouse_wheel_0.event.y = 1;
+  mouse_wheel_1 = CreateMouseWheel(2, 2);
+  mouse_wheel_1.event.x = 2;
+  mouse_wheel_1.event.y = 2;
+  EXPECT_TRUE(CanCoalesce(mouse_wheel_0, mouse_wheel_1));
+  Coalesce(mouse_wheel_0, &mouse_wheel_1);

[dtapuska, 2016/08/19 01:41:41]

Ultimately this coalescing test could probably be a little more verbose checking
the delta and the other items are added correctly..

And testing that all the conditionals of CanCoalese are tested.

[tdresser, 2016/08/19 12:43:30]

The naming here is a bit confusing.

We might want to rename the events something like mouse_wheel_old,
mouse_wheel_new.

[sahel, 2016/08/19 15:17:56]

Done.

[sahel, 2016/08/19 15:17:57]

Then naming is consistent with the rest of the unittests. I'll change the names
of the events for all unittests to be more meaningful in a separate patch. 

+  EXPECT_EQ(1, mouse_wheel_1.event.x);
+  EXPECT_EQ(1, mouse_wheel_1.event.y);
 }
 
 // Coalescing preserves the newer timestamp.