Validate that ui::Event::time_stamp comes from the same clock as TimeTicks::Now

content/browser/renderer_host/render_widget_host_view_mac_unittest.mm

 // 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_widget_host_view_mac.h"
 
 #include <Cocoa/Cocoa.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <tuple>
 
 #include "base/command_line.h"
 #include "base/mac/scoped_nsautorelease_pool.h"
 #include "base/mac/sdk_forward_declarations.h"
 #include "base/macros.h"
 #include "base/run_loop.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/test/histogram_tester.h"
+#include "base/test/simple_test_tick_clock.h"
 #include "content/browser/browser_thread_impl.h"
 #include "content/browser/compositor/test/no_transport_image_transport_factory.h"
 #include "content/browser/frame_host/render_widget_host_view_guest.h"
 #include "content/browser/gpu/compositor_util.h"
 #include "content/browser/renderer_host/render_widget_host_delegate.h"
 #include "content/common/input_messages.h"
 #include "content/common/view_messages.h"
 #include "content/public/browser/notification_types.h"
 #include "content/public/browser/render_widget_host_view_mac_delegate.h"
 #include "content/public/common/content_switches.h"
 #include "content/public/test/mock_render_process_host.h"
 #include "content/public/test/test_browser_context.h"
 #include "content/public/test/test_utils.h"
 #include "content/test/test_render_view_host.h"
 #include "gpu/ipc/common/gpu_messages.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/gtest_mac.h"
 #import "third_party/ocmock/OCMock/OCMock.h"
 #import "third_party/ocmock/ocmock_extensions.h"
+#include "ui/events/base_event_utils.h"
 #include "ui/events/latency_info.h"
 #include "ui/events/test/cocoa_test_event_utils.h"
 #import "ui/gfx/test/ui_cocoa_test_helper.h"
 
 // Helper class with methods used to mock -[NSEvent phase], used by
 // |MockScrollWheelEventWithPhase()|.
 @interface MockPhaseMethods : NSObject {
 }
 
 - (NSEventPhase)phaseBegan;
@@ skipping 169 matching lines @@
       origin.y() + line_no * size.height(),
       range.length() * size.width(),
       size.height());
 }
 
 // Returns NSScrollWheel event that mocks -phase. |mockPhaseSelector| should
 // correspond to a method in |MockPhaseMethods| that returns the desired phase.
 NSEvent* MockScrollWheelEventWithPhase(SEL mockPhaseSelector, int32_t delta) {
   CGEventRef cg_event =
       CGEventCreateScrollWheelEvent(NULL, kCGScrollEventUnitLine, 1, delta, 0);
+  CGEventTimestamp timestamp = 0;
+  CGEventSetTimestamp(cg_event, timestamp);
   NSEvent* event = [NSEvent eventWithCGEvent:cg_event];
   CFRelease(cg_event);
   method_setImplementation(
       class_getInstanceMethod([NSEvent class], @selector(phase)),
       [MockPhaseMethods instanceMethodForSelector:mockPhaseSelector]);
   return event;
 }
 
 }  // namespace
 
 class RenderWidgetHostViewMacTest : public RenderViewHostImplTestHarness {
  public:
-  RenderWidgetHostViewMacTest() : old_rwhv_(NULL), rwhv_mac_(NULL) {}
+  RenderWidgetHostViewMacTest() : old_rwhv_(NULL), rwhv_mac_(NULL) {
+    std::unique_ptr<base::SimpleTestTickClock> mock_clock(
+        new base::SimpleTestTickClock());
+    mock_clock->Advance(base::TimeDelta::FromMilliseconds(100));

[sadrul, 2016/06/23 16:38:37]

What is the purpose of this?

[majidvp, 2016/06/24 19:40:56]

If I recall correctly, there was an assert somewhere for the clock not being
zero! So I have to use a non-zero 
value which I choose 100ms.

+    ui::SetEventTickClockForTesting(std::move(mock_clock));
+  }
 
   void SetUp() override {
     RenderViewHostImplTestHarness::SetUp();
     // TestRenderViewHost's destruction assumes that its view is a
     // TestRenderWidgetHostView, so store its view and reset it back to the
     // stored view in |TearDown()|.
     old_rwhv_ = rvh()->GetWidget()->GetView();
 
     // Owned by its |cocoa_view()|, i.e. |rwhv_cocoa_|.
     rwhv_mac_ = new RenderWidgetHostViewMac(rvh()->GetWidget(), false);
@@ skipping 986 matching lines @@
   // Verify that Event.Latency.OS.MOUSE_WHEEL histogram is computed properly.
   NSEvent* wheelEvent = MockScrollWheelEventWithPhase(@selector(phaseBegan),3);
   [view->cocoa_view() scrollWheel:wheelEvent];
   histogram_tester.ExpectTotalCount("Event.Latency.OS.MOUSE_WHEEL", 1);
 
   // Clean up.
   host->ShutdownAndDestroyWidget(true);
 }
 
 }  // namespace content