--- a/dom/events/IMEStateManager.cpp
+++ b/dom/events/IMEStateManager.cpp
@@ -610,67 +610,60 @@ IMEStateManager::OnMouseButtonEventInEdi
 
   return consumed;
 }
 
 // static
 void
 IMEStateManager::OnClickInEditor(nsPresContext* aPresContext,
                                  nsIContent* aContent,
-                                 nsIDOMMouseEvent* aMouseEvent)
+                                 const WidgetMouseEvent* aMouseEvent)
 {
   MOZ_LOG(sISMLog, LogLevel::Info,
     ("OnClickInEditor(aPresContext=0x%p, aContent=0x%p, aMouseEvent=0x%p), "
      "sPresContext=0x%p, sContent=0x%p",
      aPresContext, aContent, aMouseEvent, sPresContext.get(), sContent.get()));
 
+  if (NS_WARN_IF(!aMouseEvent)) {
+    return;
+  }
+
   if (sPresContext != aPresContext || sContent != aContent) {
     MOZ_LOG(sISMLog, LogLevel::Debug,
       ("  OnClickInEditor(), "
        "the mouse event isn't fired on the editor managed by ISM"));
     return;
   }
 
   nsCOMPtr<nsIWidget> widget = aPresContext->GetRootWidget();
   NS_ENSURE_TRUE_VOID(widget);
 
-  bool isTrusted;
-  nsresult rv = aMouseEvent->AsEvent()->GetIsTrusted(&isTrusted);
-  NS_ENSURE_SUCCESS_VOID(rv);
-  if (!isTrusted) {
+  if (!aMouseEvent->IsTrusted()) {
     MOZ_LOG(sISMLog, LogLevel::Debug,
       ("  OnClickInEditor(), "
        "the mouse event isn't a trusted event"));
     return; // ignore untrusted event.
   }
 
-  int16_t button;
-  rv = aMouseEvent->GetButton(&button);
-  NS_ENSURE_SUCCESS_VOID(rv);
-  if (button != 0) {
+  if (aMouseEvent->button) {
     MOZ_LOG(sISMLog, LogLevel::Debug,
       ("  OnClickInEditor(), "
        "the mouse event isn't a left mouse button event"));
     return; // not a left click event.
   }
 
-  int32_t clickCount;
-  rv = aMouseEvent->GetDetail(&clickCount);
-  NS_ENSURE_SUCCESS_VOID(rv);
-  if (clickCount != 1) {
+  if (aMouseEvent->mClickCount != 1) {
     MOZ_LOG(sISMLog, LogLevel::Debug,
       ("  OnClickInEditor(), "
        "the mouse event isn't a single click event"));
     return; // should notify only first click event.
   }
 
-  uint16_t inputSource = nsIDOMMouseEvent::MOZ_SOURCE_UNKNOWN;
-  aMouseEvent->GetMozInputSource(&inputSource);
   InputContextAction::Cause cause =
-    inputSource == nsIDOMMouseEvent::MOZ_SOURCE_TOUCH ?
+    aMouseEvent->inputSource == nsIDOMMouseEvent::MOZ_SOURCE_TOUCH ?
       InputContextAction::CAUSE_TOUCH : InputContextAction::CAUSE_MOUSE;
 
   InputContextAction action(cause, InputContextAction::FOCUS_NOT_CHANGED);
   IMEState newState = GetNewIMEState(aPresContext, aContent);
   SetIMEState(newState, aContent, widget, action);
 }
 
 // static

--- a/dom/events/IMEStateManager.h
+++ b/dom/events/IMEStateManager.h
@@ -8,17 +8,16 @@
 #define mozilla_IMEStateManager_h_
 
 #include "mozilla/EventForwards.h"
 #include "mozilla/StaticPtr.h"
 #include "mozilla/dom/TabParent.h"
 #include "nsIWidget.h"
 
 class nsIContent;
-class nsIDOMMouseEvent;
 class nsIEditor;
 class nsINode;
 class nsPresContext;
 class nsISelection;
 
 namespace mozilla {
 
 class EventDispatchingCallback;
@@ -146,17 +145,17 @@ public:
 
   // This method is called when user clicked in an editor.
   // aContent must be:
   //   If the editor is for <input> or <textarea>, the element.
   //   If the editor is for contenteditable, the active editinghost.
   //   If the editor is for designMode, nullptr.
   static void OnClickInEditor(nsPresContext* aPresContext,
                               nsIContent* aContent,
-                              nsIDOMMouseEvent* aMouseEvent);
+                              const WidgetMouseEvent* aMouseEvent);
 
   // This method is called when editor actually gets focus.
   // aContent must be:
   //   If the editor is for <input> or <textarea>, the element.
   //   If the editor is for contenteditable, the active editinghost.
   //   If the editor is for designMode, nullptr.
   static void OnFocusInEditor(nsPresContext* aPresContext,
                               nsIContent* aContent,

--- a/editor/libeditor/EditorEventListener.cpp
+++ b/editor/libeditor/EditorEventListener.cpp
@@ -647,17 +647,17 @@ EditorEventListener::MouseClick(nsIDOMMo
   }
 
   // Notifies clicking on editor to IMEStateManager even when the event was
   // consumed.
   if (EditorHasFocus()) {
     nsPresContext* presContext = GetPresContext();
     if (presContext) {
       IMEStateManager::OnClickInEditor(presContext, GetFocusedRootContent(),
-                                       aMouseEvent);
+                                       clickEvent);
       if (DetachedFromEditor()) {
         return NS_OK;
       }
     }
   }
 
   if (DetachedFromEditorOrDefaultPrevented(clickEvent)) {
     // We're done if 'preventdefault' is true (see for example bug 70698).