From 1b2661ee753b910c183bf25170046a150f1ba7e6 Mon Sep 17 00:00:00 2001
From: Edgar Chen <echen@mozilla.com>
Date: Mon, 1 Oct 2018 09:55:42 +0000
Subject: [PATCH] Bug 1494978 - Use LookupOrAdd to simplify hashtable lookup in
 mouse event coalescence; r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D7179

--HG--
extra : moz-landing-system : lando
---
 dom/ipc/TabChild.cpp | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/dom/ipc/TabChild.cpp b/dom/ipc/TabChild.cpp
index 812f8b6256c2..5442fb1864da 100644
--- a/dom/ipc/TabChild.cpp
+++ b/dom/ipc/TabChild.cpp
@@ -1618,12 +1618,8 @@ TabChild::RecvRealMouseMoveEvent(const WidgetMouseEvent& aEvent,
                                  const uint64_t& aInputBlockId)
 {
   if (mCoalesceMouseMoveEvents && mCoalescedMouseEventFlusher) {
-    CoalescedMouseData* data = nullptr;
-    mCoalescedMouseData.Get(aEvent.pointerId, &data);
-    if (!data) {
-      data = new CoalescedMouseData();
-      mCoalescedMouseData.Put(aEvent.pointerId, data);
-    }
+    CoalescedMouseData* data = mCoalescedMouseData.LookupOrAdd(aEvent.pointerId);
+    MOZ_ASSERT(data);
     if (data->CanCoalesce(aEvent, aGuid, aInputBlockId)) {
       data->Coalesce(aEvent, aGuid, aInputBlockId);
       mCoalescedMouseEventFlusher->StartObserver();
@@ -1632,7 +1628,6 @@ TabChild::RecvRealMouseMoveEvent(const WidgetMouseEvent& aEvent,
     // Can't coalesce current mousemove event. Put the coalesced mousemove data
     // with the same pointer id to mToBeDispatchedMouseData, coalesce the
     // current one, and process all pending data in mToBeDispatchedMouseData.
-    MOZ_ASSERT(data);
     UniquePtr<CoalescedMouseData> dispatchData =
       MakeUnique<CoalescedMouseData>();