diff --git a/dom/base/nsContentUtils.cpp b/dom/base/nsContentUtils.cpp
index 43c566c4b5d8..fa987d608f6c 100644
--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -7745,11 +7745,11 @@ int16_t nsContentUtils::GetButtonsFlagForButton(int32_t aButton) {
     case -1:
       return MouseButtonsFlag::eNoButtons;
     case MouseButton::ePrimary:
-      return MouseButtonsFlag::eLeftFlag;
+      return MouseButtonsFlag::ePrimaryFlag;
     case MouseButton::eMiddle:
       return MouseButtonsFlag::eMiddleFlag;
     case MouseButton::eSecondary:
-      return MouseButtonsFlag::eRightFlag;
+      return MouseButtonsFlag::eSecondaryFlag;
     case 4:
       return MouseButtonsFlag::e4thFlag;
     case 5:
diff --git a/dom/events/PointerEventHandler.cpp b/dom/events/PointerEventHandler.cpp
index 052c2d49b4f2..a8b062f4e87a 100644
--- a/dom/events/PointerEventHandler.cpp
+++ b/dom/events/PointerEventHandler.cpp
@@ -451,7 +451,7 @@ void PointerEventHandler::InitPointerEventFromTouch(
 
   int16_t buttons = aTouchEvent->mMessage == eTouchEnd
                         ? MouseButtonsFlag::eNoButtons
-                        : MouseButtonsFlag::eLeftFlag;
+                        : MouseButtonsFlag::ePrimaryFlag;
 
   aPointerEvent->mIsPrimary = aIsPrimary;
   aPointerEvent->pointerId = aTouch->Identifier();
diff --git a/dom/html/HTMLInputElement.cpp b/dom/html/HTMLInputElement.cpp
index 468dfdfa6f09..4cfe2e7afb8f 100644
--- a/dom/html/HTMLInputElement.cpp
+++ b/dom/html/HTMLInputElement.cpp
@@ -4104,7 +4104,7 @@ void HTMLInputElement::PostHandleEventForRangeThumb(
       }
       if (aVisitor.mEvent->mMessage == eMouseDown) {
         if (aVisitor.mEvent->AsMouseEvent()->mButtons ==
-            MouseButtonsFlag::eLeftFlag) {
+            MouseButtonsFlag::ePrimaryFlag) {
           StartRangeThumbDrag(inputEvent);
         } else if (mIsDraggingRange) {
           CancelRangeThumbDrag();
diff --git a/gfx/layers/apz/src/APZCTreeManager.cpp b/gfx/layers/apz/src/APZCTreeManager.cpp
index 593f3d2bf270..c2531a2e5afa 100644
--- a/gfx/layers/apz/src/APZCTreeManager.cpp
+++ b/gfx/layers/apz/src/APZCTreeManager.cpp
@@ -2128,7 +2128,7 @@ APZEventResult APZCTreeManager::ProcessTouchInputForScrollbarDrag(
   MouseInput mouseInput{MultiTouchTypeToMouseType(aTouchInput.mType),
                         MouseInput::LEFT_BUTTON,
                         dom::MouseEvent_Binding::MOZ_SOURCE_TOUCH,
-                        MouseButtonsFlag::eLeftFlag,
+                        MouseButtonsFlag::ePrimaryFlag,
                         aTouchInput.mTouches[0].mScreenPoint,
                         aTouchInput.mTime,
                         aTouchInput.mTimeStamp,
diff --git a/widget/EventForwards.h b/widget/EventForwards.h
index bd08ec616948..d95dbf32f198 100644
--- a/widget/EventForwards.h
+++ b/widget/EventForwards.h
@@ -447,8 +447,8 @@ enum MouseButton {
 
 enum MouseButtonsFlag {
   eNoButtons = 0x00,
-  eLeftFlag = 0x01,
-  eRightFlag = 0x02,
+  ePrimaryFlag = 0x01,
+  eSecondaryFlag = 0x02,
   eMiddleFlag = 0x04,
   // typicall, "back" button being left side of 5-button
   // mice, see "buttons" attribute document of DOM3 Events.
diff --git a/widget/MouseEvents.h b/widget/MouseEvents.h
index f37826b81005..8cc40e5b4583 100644
--- a/widget/MouseEvents.h
+++ b/widget/MouseEvents.h
@@ -135,10 +135,10 @@ class WidgetMouseEventBase : public WidgetInputEvent {
   uint16_t mInputSource;
 
   bool IsLeftButtonPressed() const {
-    return !!(mButtons & MouseButtonsFlag::eLeftFlag);
+    return !!(mButtons & MouseButtonsFlag::ePrimaryFlag);
   }
   bool IsRightButtonPressed() const {
-    return !!(mButtons & MouseButtonsFlag::eRightFlag);
+    return !!(mButtons & MouseButtonsFlag::eSecondaryFlag);
   }
   bool IsMiddleButtonPressed() const {
     return !!(mButtons & MouseButtonsFlag::eMiddleFlag);
diff --git a/widget/android/nsWindow.cpp b/widget/android/nsWindow.cpp
index 87924633283a..2a42ba7da3a1 100644
--- a/widget/android/nsWindow.cpp
+++ b/widget/android/nsWindow.cpp
@@ -579,10 +579,10 @@ class nsWindow::NPZCSupport final
     int16_t result = 0;
 
     if (buttons & java::sdk::MotionEvent::BUTTON_PRIMARY) {
-      result |= MouseButtonsFlag::eLeftFlag;
+      result |= MouseButtonsFlag::ePrimaryFlag;
     }
     if (buttons & java::sdk::MotionEvent::BUTTON_SECONDARY) {
-      result |= MouseButtonsFlag::eRightFlag;
+      result |= MouseButtonsFlag::eSecondaryFlag;
     }
     if (buttons & java::sdk::MotionEvent::BUTTON_TERTIARY) {
       result |= MouseButtonsFlag::eMiddleFlag;
diff --git a/widget/cocoa/nsChildView.mm b/widget/cocoa/nsChildView.mm
index 0ac1b18c5c00..bff7de810800 100644
--- a/widget/cocoa/nsChildView.mm
+++ b/widget/cocoa/nsChildView.mm
@@ -3631,10 +3631,10 @@ static gfx::IntPoint GetIntegerDeltaForEvent(NSEvent* aEvent) {
   NSUInteger mouseButtons = [NSEvent pressedMouseButtons];
 
   if (mouseButtons & 0x01) {
-    mouseEvent->mButtons |= MouseButtonsFlag::eLeftFlag;
+    mouseEvent->mButtons |= MouseButtonsFlag::ePrimaryFlag;
   }
   if (mouseButtons & 0x02) {
-    mouseEvent->mButtons |= MouseButtonsFlag::eRightFlag;
+    mouseEvent->mButtons |= MouseButtonsFlag::eSecondaryFlag;
   }
   if (mouseButtons & 0x04) {
     mouseEvent->mButtons |= MouseButtonsFlag::eMiddleFlag;
diff --git a/widget/gtk/nsGtkKeyUtils.cpp b/widget/gtk/nsGtkKeyUtils.cpp
index c03119a54dd5..5f2930a37ab4 100644
--- a/widget/gtk/nsGtkKeyUtils.cpp
+++ b/widget/gtk/nsGtkKeyUtils.cpp
@@ -1065,26 +1065,27 @@ void KeymapWrapper::InitInputEvent(WidgetInputEvent& aInputEvent,
   WidgetMouseEventBase& mouseEvent = *aInputEvent.AsMouseEventBase();
   mouseEvent.mButtons = 0;
   if (aModifierState & GDK_BUTTON1_MASK) {
-    mouseEvent.mButtons |= MouseButtonsFlag::eLeftFlag;
+    mouseEvent.mButtons |= MouseButtonsFlag::ePrimaryFlag;
   }
   if (aModifierState & GDK_BUTTON3_MASK) {
-    mouseEvent.mButtons |= MouseButtonsFlag::eRightFlag;
+    mouseEvent.mButtons |= MouseButtonsFlag::eSecondaryFlag;
   }
   if (aModifierState & GDK_BUTTON2_MASK) {
     mouseEvent.mButtons |= MouseButtonsFlag::eMiddleFlag;
   }
 
   if (doLog) {
-    MOZ_LOG(gKeymapWrapperLog, LogLevel::Debug,
-            ("%p InitInputEvent, aInputEvent has mButtons, "
-             "aInputEvent.mButtons=0x%04X (Left: %s, Right: %s, Middle: %s, "
-             "4th (BACK): %s, 5th (FORWARD): %s)",
-             keymapWrapper, mouseEvent.mButtons,
-             GetBoolName(mouseEvent.mButtons & MouseButtonsFlag::eLeftFlag),
-             GetBoolName(mouseEvent.mButtons & MouseButtonsFlag::eRightFlag),
-             GetBoolName(mouseEvent.mButtons & MouseButtonsFlag::eMiddleFlag),
-             GetBoolName(mouseEvent.mButtons & MouseButtonsFlag::e4thFlag),
-             GetBoolName(mouseEvent.mButtons & MouseButtonsFlag::e5thFlag)));
+    MOZ_LOG(
+        gKeymapWrapperLog, LogLevel::Debug,
+        ("%p InitInputEvent, aInputEvent has mButtons, "
+         "aInputEvent.mButtons=0x%04X (Left: %s, Right: %s, Middle: %s, "
+         "4th (BACK): %s, 5th (FORWARD): %s)",
+         keymapWrapper, mouseEvent.mButtons,
+         GetBoolName(mouseEvent.mButtons & MouseButtonsFlag::ePrimaryFlag),
+         GetBoolName(mouseEvent.mButtons & MouseButtonsFlag::eSecondaryFlag),
+         GetBoolName(mouseEvent.mButtons & MouseButtonsFlag::eMiddleFlag),
+         GetBoolName(mouseEvent.mButtons & MouseButtonsFlag::e4thFlag),
+         GetBoolName(mouseEvent.mButtons & MouseButtonsFlag::e5thFlag)));
   }
 }
 
diff --git a/widget/windows/KeyboardLayout.cpp b/widget/windows/KeyboardLayout.cpp
index 307720e75829..798f73f54d2b 100644
--- a/widget/windows/KeyboardLayout.cpp
+++ b/widget/windows/KeyboardLayout.cpp
@@ -918,10 +918,10 @@ void ModifierKeyState::InitMouseEvent(WidgetInputEvent& aMouseEvent) const {
   WidgetMouseEventBase& mouseEvent = *aMouseEvent.AsMouseEventBase();
   mouseEvent.mButtons = 0;
   if (::GetKeyState(VK_LBUTTON) < 0) {
-    mouseEvent.mButtons |= MouseButtonsFlag::eLeftFlag;
+    mouseEvent.mButtons |= MouseButtonsFlag::ePrimaryFlag;
   }
   if (::GetKeyState(VK_RBUTTON) < 0) {
-    mouseEvent.mButtons |= MouseButtonsFlag::eRightFlag;
+    mouseEvent.mButtons |= MouseButtonsFlag::eSecondaryFlag;
   }
   if (::GetKeyState(VK_MBUTTON) < 0) {
     mouseEvent.mButtons |= MouseButtonsFlag::eMiddleFlag;
diff --git a/widget/windows/TSFTextStore.cpp b/widget/windows/TSFTextStore.cpp
index 0f64c7c721b8..947be3c6b2eb 100644
--- a/widget/windows/TSFTextStore.cpp
+++ b/widget/windows/TSFTextStore.cpp
@@ -557,10 +557,10 @@ static nsCString GetMouseButtonsName(int16_t aButtons) {
     return NS_LITERAL_CSTRING("no buttons");
   }
   nsCString names;
-  if (aButtons & MouseButtonsFlag::eLeftFlag) {
+  if (aButtons & MouseButtonsFlag::ePrimaryFlag) {
     names = "LeftButton";
   }
-  if (aButtons & MouseButtonsFlag::eRightFlag) {
+  if (aButtons & MouseButtonsFlag::eSecondaryFlag) {
     ADD_SEPARATOR_IF_NECESSARY(names);
     names += "RightButton";
   }
diff --git a/widget/windows/nsWindow.cpp b/widget/windows/nsWindow.cpp
index 9527b9ea23b6..612a99418057 100644
--- a/widget/windows/nsWindow.cpp
+++ b/widget/windows/nsWindow.cpp
@@ -8617,8 +8617,8 @@ bool nsWindow::OnPointerEvents(UINT msg, WPARAM aWParam, LPARAM aLParam) {
   // 1024. Convert it to float.
   float pressure = penInfo.pressure ? (float)penInfo.pressure / 1024 : 0;
   int16_t buttons = sPointerDown ? button == MouseButton::ePrimary
-                                       ? MouseButtonsFlag::eLeftFlag
-                                       : MouseButtonsFlag::eRightFlag
+                                       ? MouseButtonsFlag::ePrimaryFlag
+                                       : MouseButtonsFlag::eSecondaryFlag
                                  : MouseButtonsFlag::eNoButtons;
   WinPointerInfo pointerInfo(pointerId, penInfo.tiltX, penInfo.tiltY, pressure,
                              buttons);