[snapshot] Make the API external reference table const.

Chromium side: https://chromium-review.googlesource.com/c/chromium/src/+/639552

Bug: chromium:759831
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: I1b217c4fa4c930733dcfab982879bf41936a3a83
Reviewed-on: https://chromium-review.googlesource.com/639551
Commit-Queue: Jeremy Roman <jbroman@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47683}

include/v8.h

@@ -6830,7 +6830,7 @@ class V8_EXPORT Isolate {
      * deserialization. This array and its content must stay valid for the
      * entire lifetime of the isolate.
      */
-    intptr_t* external_references;
+    const intptr_t* external_references;
 
     /**
      * Whether calling Atomics.wait (a function that may block) is allowed in
@@ -8175,7 +8175,7 @@ class V8_EXPORT SnapshotCreator {
    * \param external_references a null-terminated array of external references
    *        that must be equivalent to CreateParams::external_references.
    */
-  SnapshotCreator(intptr_t* external_references = nullptr,
+  SnapshotCreator(const intptr_t* external_references = nullptr,
                   StartupData* existing_blob = nullptr);
 
   ~SnapshotCreator();

src/api.cc

@@ -563,7 +563,7 @@ struct SnapshotCreatorData {
 
 }  // namespace
 
-SnapshotCreator::SnapshotCreator(intptr_t* external_references,
+SnapshotCreator::SnapshotCreator(const intptr_t* external_references,
                                  StartupData* existing_snapshot) {
   i::Isolate* internal_isolate = new i::Isolate(true);
   Isolate* isolate = reinterpret_cast<Isolate*>(internal_isolate);

src/isolate.h

@@ -430,7 +430,7 @@ typedef std::vector<HeapObject*> DebugObjectCache;
   V(DebugObjectCache*, string_stream_debug_object_cache, nullptr)             \
   V(Object*, string_stream_current_security_token, nullptr)                   \
   V(ExternalReferenceTable*, external_reference_table, nullptr)               \
-  V(intptr_t*, api_external_references, nullptr)                              \
+  V(const intptr_t*, api_external_references, nullptr)                        \
   V(AddressToIndexHashMap*, external_reference_map, nullptr)                  \
   V(HeapObjectToIndexHashMap*, root_index_map, nullptr)                       \
   V(int, pending_microtask_count, 0)                                          \

src/snapshot/serializer-common.cc

@@ -33,7 +33,7 @@ ExternalReferenceEncoder::ExternalReferenceEncoder(Isolate* isolate) {
     DCHECK(map_->Get(addr).IsJust());
   }
   // Add external references provided by the embedder.
-  intptr_t* api_references = isolate->api_external_references();
+  const intptr_t* api_references = isolate->api_external_references();
   if (api_references == nullptr) return;
   for (uint32_t i = 0; api_references[i] != 0; ++i) {
     Address addr = reinterpret_cast<Address>(api_references[i]);

src/snapshot/serializer-common.h

@@ -48,7 +48,7 @@ class ExternalReferenceEncoder {
 
 #ifdef DEBUG
   std::vector<int> count_;
-  intptr_t* api_references_;
+  const intptr_t* api_references_;
 #endif  // DEBUG
 
   DISALLOW_COPY_AND_ASSIGN(ExternalReferenceEncoder);