Remove use of deprecated function v8::V8::SetNativesDataBlob

With the recent port of the streams API to C++ [0], the natives blob is
now unused and will shortly be removed. V8 API related to the natives
blob is being deprecated [1] and will be removed in the next release.

This CL is the minimal change to keep up with these API deprecations.

In follow-up work, all other infrastructure related to the natives blob
should be removed.

[0] https://crrev.com/c/1746118
[1] https://crrev.com/c/1824944

Bug: v8:7624
Change-Id: I26e409660d177035cdb5d92c317fc2e0174be2f7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1834352Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702475}

gin/v8_initializer.cc

@@ -266,9 +266,9 @@ void V8Initializer::Initialize(IsolateHolder::ScriptMode mode) {
   }
 
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+  // TODO(v8:7624): Remove natives and all remaining infrastructure.
   v8::StartupData natives;
   GetMappedFileData(g_mapped_natives, &natives);
-  v8::V8::SetNativesDataBlob(&natives);
 
   if (g_mapped_snapshot) {
     v8::StartupData snapshot;

pdf/pdf_ppapi.cc

@@ -43,13 +43,13 @@ bool PDFModule::Init() {
 
 pp::Instance* PDFModule::CreateInstance(PP_Instance instance) {
   if (!g_sdk_initialized_via_pepper) {
+    // TODO(v8:7624): Remove natives and all remaining infrastructure.
     v8::StartupData natives;
     v8::StartupData snapshot;
     pp::PDF::GetV8ExternalSnapshotData(pp::InstanceHandle(instance),
                                        &natives.data, &natives.raw_size,
                                        &snapshot.data, &snapshot.raw_size);
     if (natives.data) {
-      v8::V8::SetNativesDataBlob(&natives);
       v8::V8::SetSnapshotDataBlob(&snapshot);
     }
     InitializeSDK(/*enable_v8=*/true);