RPP: remove DOMRect dependency from trace engine

It means any NodeJS consumers (e.g. Lighthouse) have to polyfill
`DOMRect`. Given that we only use this to store the x, y, width, height,
it seems silly to force NodeJS users to jump through this hoop.

R=alexrudenko@chromium.org

Bug: 441265851
Change-Id: Ib6aa54b33ec2615dd34b30a0cc329202ada76b6d
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6889752
Commit-Queue: Jack Franklin <jacktfranklin@chromium.org>
Auto-Submit: Jack Franklin <jacktfranklin@chromium.org>
Reviewed-by: Alex Rudenko <alexrudenko@chromium.org>
Commit-Queue: Alex Rudenko <alexrudenko@chromium.org>

Author: jackfranklin

front_end/models/trace/handlers/MetaHandler.ts

@@ -22,7 +22,7 @@ let browserProcessId: Types.Events.ProcessID = Types.Events.ProcessID(-1);
 let browserThreadId: Types.Events.ThreadID = Types.Events.ThreadID(-1);
 let gpuProcessId: Types.Events.ProcessID = Types.Events.ProcessID(-1);
 let gpuThreadId: Types.Events.ThreadID = Types.Events.ThreadID(-1);
-let viewportRect: DOMRect|null = null;
+let viewportRect: {x: number, y: number, width: number, height: number}|null = null;
 let devicePixelRatio: number|null = null;
 
 const processNames = new Map<Types.Events.ProcessID, Types.Events.ProcessName>();
@@ -181,7 +181,7 @@ export function handleEvent(event: Types.Events.Event): void {
     const viewportY = rectAsArray[1];
     const viewportWidth = rectAsArray[2];
     const viewportHeight = rectAsArray[5];
-    viewportRect = new DOMRect(viewportX, viewportY, viewportWidth, viewportHeight);
+    viewportRect = {x: viewportX, y: viewportY, width: viewportWidth, height: viewportHeight};
     devicePixelRatio = event.args.data.dpr;
   }
 
@@ -466,7 +466,7 @@ export interface MetaHandlerData {
   frameByProcessId: Map<Types.Events.ProcessID, Map<string, Types.Events.TraceFrame>>;
   mainFrameNavigations: Types.Events.NavigationStart[];
   gpuThreadId?: Types.Events.ThreadID;
-  viewportRect?: DOMRect;
+  viewportRect?: {x: number, y: number, width: number, height: number};
   devicePixelRatio?: number;
 }