Issue #1916 - Part 1: Convert flags passed to ReflowChild, FinishReflowChild, etc into an enum class.

Backported from Mozilla bug 1571250.

layout/forms/nsNumberControlFrame.cpp

@@ -181,8 +181,8 @@ nsNumberControlFrame::Reflow(nsPresContext* aPresContext,
     // will be fixed later.
     const nsSize dummyContainerSize;
     ReflowChild(outerWrapperFrame, aPresContext, wrappersDesiredSize,
-                wrapperReflowInput, myWM, wrapperOffset, dummyContainerSize, 0,
-                childStatus);
+                wrapperReflowInput, myWM, wrapperOffset, dummyContainerSize,
+                ReflowChildFlags::Default, childStatus);
     MOZ_ASSERT(NS_FRAME_IS_FULLY_COMPLETE(childStatus),
                "We gave our child unconstrained available block-size, "
                "so it should be complete");
@@ -219,8 +219,8 @@ nsNumberControlFrame::Reflow(nsPresContext* aPresContext,
 
     // Place the child
     FinishReflowChild(outerWrapperFrame, aPresContext, wrappersDesiredSize,
-                      &wrapperReflowInput, myWM, wrapperOffset,
-                      borderBoxSize, 0);
+                      &wrapperReflowInput, myWM, wrapperOffset, borderBoxSize,
+                      ReflowChildFlags::Default);
 
     nsSize contentBoxSize =
       LogicalSize(myWM, contentBoxISize, contentBoxBSize).