properly add lengthComputable flag to XHR sync path

src/browser/webapi/event/ProgressEvent.zig

@@ -62,6 +62,7 @@ fn initWithTrusted(arena: *lp.Arena, typ: String, _opts: ?Options, trusted: bool
             ._proto = undefined,
             ._total = opts.total,
             ._loaded = opts.loaded,
+            ._length_computable = opts.lengthComputable,
         },
     );
 

src/browser/webapi/net/XMLHttpRequest.zig

@@ -348,8 +348,8 @@ pub fn send(self: *XMLHttpRequest, body_: ?BodyInit, exec_: *const Execution) !v
 
     try self.stateChanged(.done, exec);
     const loaded = self._response_data.items.len;
-    try self._proto.dispatch(.load, .{ .total = loaded, .loaded = loaded }, exec);
-    try self._proto.dispatch(.load_end, .{ .total = loaded, .loaded = loaded }, exec);
+    try self._proto.dispatch(.load, .{ .total = loaded, .loaded = loaded, .length_computable = true }, exec);
+    try self._proto.dispatch(.load_end, .{ .total = loaded, .loaded = loaded, .length_computable = true }, exec);
 
     log.info(.http, "request complete", .{
         .source = "xhr",

src/browser/webapi/net/XMLHttpRequestEventTarget.zig

@@ -74,7 +74,11 @@ pub fn dispatch(self: *XMLHttpRequestEventTarget, comptime event_type: DispatchT
     const progress = progress_ orelse Progress{};
     const event = (try ProgressEvent.initTrusted(
         comptime .wrap(typ),
-        .{ .total = progress.total, .loaded = progress.loaded },
+        .{
+            .total = progress.total,
+            .loaded = progress.loaded,
+            .lengthComputable = progress.length_computable,
+        },
         exec.page,
     )).asEvent();
 
@@ -173,6 +177,7 @@ const DispatchType = enum {
 const Progress = struct {
     loaded: usize = 0,
     total: usize = 0,
+    length_computable: bool = false,
 };
 
 pub const JsApi = struct {