Hide ExternalStringData when possible

With V8's recent change https://crrev.com/c/6235575 , the storage for
each external string is now reported in a separate node from the string.
This is important for correctness in the case where multiple external
strings refer to the same backing storage. However, in the vast majority
of cases, the storage has only one owning string, so we can improve the
readability of snapshots by subsuming the backing storage size into the
string instance.

Bug: 41448424
Change-Id: I5f635eae7aa710f583eeb9ba4196d3e513262916
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6234887
Reviewed-by: Simon Zünd <[email protected]>
Commit-Queue: Seth Brenith <[email protected]>

Author: sethbrenith

front_end/entrypoints/heap_snapshot_worker/HeapSnapshot.ts

@@ -3145,7 +3145,7 @@ export class JSHeapSnapshot extends HeapSnapshot {
 
     const node = this.createNode(0);
     for (let i = 0; i < nodeCount; ++i) {
-      if (node.isHidden() || node.isArray()) {
+      if (node.isHidden() || node.isArray() || (node.isNative() && node.rawName() === 'system / ExternalStringData')) {
         owners[i] = kUnvisited;
       } else {
         // The node owns itself.
@@ -3652,6 +3652,10 @@ export class JSHeapSnapshotNode extends HeapSnapshotNode {
     return this.rawType() === this.snapshot.nodeSyntheticType;
   }
 
+  isNative(): boolean {
+    return this.rawType() === this.snapshot.nodeNativeType;
+  }
+
   override isUserRoot(): boolean {
     return !this.isSynthetic();
   }