Bug 1694229 - Separate Enter/Exit Widget Events from Mouse Button events r=smaug

If we don't do this, then just moving the mouse over a window experiencing a
slow script will cause it to show the notification. We could try to
deserialize the message inside nsContentUtils::IsMessageCriticalInputEvent, but
that seems overcomplicated compared to just adding a new message which proxies
to the original message handlers.

Differential Revision: https://phabricator.services.mozilla.com/D106016

dom/base/nsContentUtils.cpp

@@ -10019,6 +10019,7 @@ bool nsContentUtils::IsMessageInputEvent(const IPC::Message& aMsg) {
     switch (aMsg.type()) {
       case mozilla::dom::PBrowser::Msg_RealMouseMoveEvent__ID:
       case mozilla::dom::PBrowser::Msg_RealMouseButtonEvent__ID:
+      case mozilla::dom::PBrowser::Msg_RealMouseEnterExitWidgetEvent__ID:
       case mozilla::dom::PBrowser::Msg_RealKeyEvent__ID:
       case mozilla::dom::PBrowser::Msg_MouseWheelEvent__ID:
       case mozilla::dom::PBrowser::Msg_RealTouchEvent__ID:

dom/ipc/BrowserChild.cpp

@@ -1679,6 +1679,19 @@ mozilla::ipc::IPCResult BrowserChild::RecvNormalPriorityRealMouseButtonEvent(
   return RecvRealMouseButtonEvent(aEvent, aGuid, aInputBlockId);
 }
 
+mozilla::ipc::IPCResult BrowserChild::RecvRealMouseEnterExitWidgetEvent(
+    const WidgetMouseEvent& aEvent, const ScrollableLayerGuid& aGuid,
+    const uint64_t& aInputBlockId) {
+  return RecvRealMouseButtonEvent(aEvent, aGuid, aInputBlockId);
+}
+
+mozilla::ipc::IPCResult
+BrowserChild::RecvNormalPriorityRealMouseEnterExitWidgetEvent(
+    const WidgetMouseEvent& aEvent, const ScrollableLayerGuid& aGuid,
+    const uint64_t& aInputBlockId) {
+  return RecvRealMouseButtonEvent(aEvent, aGuid, aInputBlockId);
+}
+
 // In case handling repeated mouse wheel takes much time, we skip firing current
 // wheel event if it may be coalesced to the next one.
 bool BrowserChild::MaybeCoalesceWheelEvent(const WidgetWheelEvent& aEvent,

dom/ipc/BrowserChild.h

@@ -329,6 +329,13 @@ class BrowserChild final : public nsMessageManagerScriptExecutor,
       const mozilla::WidgetMouseEvent& aEvent, const ScrollableLayerGuid& aGuid,
       const uint64_t& aInputBlockId);
 
+  mozilla::ipc::IPCResult RecvRealMouseEnterExitWidgetEvent(
+      const mozilla::WidgetMouseEvent& aEvent, const ScrollableLayerGuid& aGuid,
+      const uint64_t& aInputBlockId);
+  mozilla::ipc::IPCResult RecvNormalPriorityRealMouseEnterExitWidgetEvent(
+      const mozilla::WidgetMouseEvent& aEvent, const ScrollableLayerGuid& aGuid,
+      const uint64_t& aInputBlockId);
+
   MOZ_CAN_RUN_SCRIPT_BOUNDARY
   mozilla::ipc::IPCResult RecvRealDragEvent(const WidgetDragEvent& aEvent,
                                             const uint32_t& aDragAction,

dom/ipc/BrowserParent.cpp

@@ -1462,10 +1462,10 @@ void BrowserParent::SendRealMouseEvent(WidgetMouseEvent& aEvent) {
     localEvent.mMessage = eMouseEnterIntoWidget;
     DebugOnly<bool> ret =
         isInputPriorityEventEnabled
-            ? SendRealMouseButtonEvent(localEvent, guid, blockId)
+            ? SendRealMouseEnterExitWidgetEvent(localEvent, guid, blockId)
-            : SendNormalPriorityRealMouseButtonEvent(localEvent, guid, blockId);
+            : SendNormalPriorityRealMouseEnterExitWidgetEvent(localEvent, guid,
-    NS_WARNING_ASSERTION(
+                                                              blockId);
-        ret, "SendRealMouseButtonEvent(eMouseEnterIntoWidget) failed");
+    NS_WARNING_ASSERTION(ret, "SendRealMouseEnterExitWidgetEvent() failed");
     MOZ_ASSERT(!ret || localEvent.HasBeenPostedToRemoteProcess());
   }
 
@@ -1500,6 +1500,18 @@ void BrowserParent::SendRealMouseEvent(WidgetMouseEvent& aEvent) {
     return;
   }
 
+  if (eMouseEnterIntoWidget == aEvent.mMessage ||
+      eMouseExitFromWidget == aEvent.mMessage) {
+    DebugOnly<bool> ret =
+        isInputPriorityEventEnabled
+            ? SendRealMouseEnterExitWidgetEvent(aEvent, guid, blockId)
+            : SendNormalPriorityRealMouseEnterExitWidgetEvent(aEvent, guid,
+                                                              blockId);
+    NS_WARNING_ASSERTION(ret, "SendRealMouseEnterExitWidgetEvent() failed");
+    MOZ_ASSERT(!ret || aEvent.HasBeenPostedToRemoteProcess());
+    return;
+  }
+
   DebugOnly<bool> ret =
       isInputPriorityEventEnabled
           ? SendRealMouseButtonEvent(aEvent, guid, blockId)

dom/ipc/PBrowser.ipdl

@@ -792,6 +792,14 @@ child:
                                              ScrollableLayerGuid aGuid,
                                              uint64_t aInputBlockId);
 
+    [Priority=input]
+    async RealMouseEnterExitWidgetEvent(WidgetMouseEvent event,
+                                                    ScrollableLayerGuid aGuid,
+                                                    uint64_t aInputBlockId);
+    async NormalPriorityRealMouseEnterExitWidgetEvent(WidgetMouseEvent event,
+                                                      ScrollableLayerGuid aGuid,
+                                                      uint64_t aInputBlockId);
+
     [Priority=input]
     async RealKeyEvent(WidgetKeyboardEvent event);
     async NormalPriorityRealKeyEvent(WidgetKeyboardEvent event);