[web snapshots / d8] Make the output file name configurable

Bug: v8:11525
Change-Id: I16191bfa03bb9bbfb57a48015244c780e8cf30e1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3217190Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77311}

src/d8/d8.cc

@@ -745,6 +745,11 @@ bool Shell::ExecuteString(Isolate* isolate, Local<String> source,
     data->realm_current_ = data->realm_switch_;
 
     if (options.web_snapshot_config) {
+      const char* web_snapshot_output_file_name = "web.snap";
+      if (options.web_snapshot_output) {
+        web_snapshot_output_file_name = options.web_snapshot_output;
+      }
+
       MaybeLocal<PrimitiveArray> maybe_exports =
           ReadLines(isolate, options.web_snapshot_config);
       Local<PrimitiveArray> exports;
@@ -759,12 +764,17 @@ bool Shell::ExecuteString(Isolate* isolate, Local<String> source,
       i::WebSnapshotData snapshot_data;
       if (serializer.TakeSnapshot(context, exports, snapshot_data)) {
         DCHECK_NOT_NULL(snapshot_data.buffer);
-        WriteChars("web.snap", snapshot_data.buffer, snapshot_data.buffer_size);
+        WriteChars(web_snapshot_output_file_name, snapshot_data.buffer,
+                   snapshot_data.buffer_size);
       } else {
         CHECK(try_catch.HasCaught());
         ReportException(isolate, &try_catch);
         return false;
       }
+    } else if (options.web_snapshot_output) {
+      isolate->ThrowError(
+          "Web snapshots: --web-snapshot-config is needed when "
+          "--web-snapshot-output is passed");
     }
   }
   Local<Value> result;
@@ -4360,6 +4370,9 @@ bool Shell::SetOptions(int argc, char* argv[]) {
     } else if (strncmp(argv[i], "--web-snapshot-config=", 22) == 0) {
       options.web_snapshot_config = argv[i] + 22;
       argv[i] = nullptr;
+    } else if (strncmp(argv[i], "--web-snapshot-output=", 22) == 0) {
+      options.web_snapshot_output = argv[i] + 22;
+      argv[i] = nullptr;
     } else if (strcmp(argv[i], "--experimental-d8-web-snapshot-api") == 0) {
       options.d8_web_snapshot_api = true;
       argv[i] = nullptr;

src/d8/d8.h

@@ -436,6 +436,8 @@ class ShellOptions {
       "enable-system-instrumentation", false};
   DisallowReassignment<const char*> web_snapshot_config = {
       "web-snapshot-config", nullptr};
+  DisallowReassignment<const char*> web_snapshot_output = {
+      "web-snapshot-output", nullptr};
   DisallowReassignment<bool> d8_web_snapshot_api = {
       "experimental-d8-web-snapshot-api", false};
   DisallowReassignment<bool> compile_only = {"compile-only", false};