[wasm] Add experimental wasm threads to COOP+COEP features.

Bug: chromium:1167733
Change-Id: Ie057068ee4ff08055d9dc7812a2e4f4dca9ec8d9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2636844Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72239}

src/api/api.cc

@@ -6026,6 +6026,7 @@ void V8::GetSharedMemoryStatistics(SharedMemoryStatistics* statistics) {
 
 void V8::SetIsCrossOriginIsolated() {
   i::FLAG_harmony_sharedarraybuffer = true;
+  i::FLAG_experimental_wasm_threads = true;
 }
 
 template <typename ObjectType>