In r396490, the MSG used in EventTest.EventLatencyOSMouseWheelHistogram is not properly initialized, and DrMemory complains:

https://build.chromium.org/p/chromium.memory.fyi/builders/Windows%20Unit%20%28DrMemory%20full%29%20%285%29/builds/7358

UNINITIALIZED READ: reading register ecx
# 0 USER32.dll!gapfnScSendMessage                                             +0x1ce    (0x750d6196 <USER32.dll+0x16196>)
# 1 USER32.dll!ScreenToClient                                                 +0x13     (0x750e2291 <USER32.dll+0x22291>)
# 2 events.dll!ui::EventLocationFromNative                                     [ui\events\win\events_win.cc:250]
# 3 events.dll!ui::LocatedEvent::LocatedEvent                                  [ui\events\event.cc:432]
# 4 events.dll!ui::MouseEvent::MouseEvent                                      [ui\events\event.cc:460]
# 5 events.dll!ui::MouseWheelEvent::MouseWheelEvent                            [ui\events\event.cc:605]
# 6 ui::EventTest_EventLatencyOSMouseWheelHistogram_Test::TestBody             [ui\events\event_unittest.cc:925]
# 7 testing::internal::HandleExceptionsInMethodIfSupported<>                   [testing\gtest\src\gtest.cc:2458]
Note: @0:00:09.360 in thread 3776
Note: instruction: test   %ecx %ecx
Suppression (error hash=#447C0707F2888654#):
For more info on using suppressions see http://dev.chromium.org/developers/how-tos/using-drmemory#TOC-Suppressing-error-reports-from-the-
{
UNINITIALIZED READ
name=<insert_a_suppression_name_here>
USER32.dll!gapfnScSendMessage
USER32.dll!ScreenToClient
events.dll!ui::EventLocationFromNative
events.dll!ui::LocatedEvent::LocatedEvent
events.dll!ui::MouseEvent::MouseEvent
events.dll!ui::MouseWheelEvent::MouseWheelEvent
*!ui::EventTest_EventLatencyOSMouseWheelHistogram_Test::TestBody
*!testing::internal::HandleExceptionsInMethodIfSupported<>
}