[tools][system-analyzer] Fix Chunk Positions

This CL fixes the bug related with chunk position initialisation.
The bug caused by not subtracting the timeline chunk start time from
chunk start time. Additionally, it corrects the offset being used while
detecting the chunk location.

Bug: v8:10644

Change-Id: Icf426a297402f87d2acda0b2aa747b90e91686c6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2377740Reviewed-by: Sathya Gunasekaran  <gsathya@chromium.org>
Commit-Queue: Zeynep Cankara <zcankara@google.com>
Cr-Commit-Position: refs/heads/master@{#69589}

tools/system-analyzer/map-processor.mjs

@@ -337,7 +337,7 @@ class MapLogEvent extends Event {
 
   position(chunks) {
     let index = this.chunkIndex(chunks);
-    let xFrom = (index + 0.5) * kChunkWidth;
+    let xFrom = (index + 1.5) * kChunkWidth;
     let yFrom = kChunkHeight - chunks[index].yOffset(this);
     return [xFrom, yFrom];
   }

tools/system-analyzer/timeline/timeline-track.mjs

@@ -240,7 +240,7 @@ defineCustomElement('./timeline/timeline-track', (templateText) =>
         if (chunk.isEmpty()) continue;
         let node = this.div();
         node.className = 'chunk';
-        node.style.left = (chunks[i].start * this.#timeToPixel) + 'px';
+        node.style.left = ((chunks[i].start - start) * this.#timeToPixel) + 'px';
         node.style.height = height + 'px';
         node.chunk = chunk;
         node.addEventListener('mousemove', e => this.handleChunkMouseMove(e));