[gin] Make a new IsolateHolder ctor for snapshot

gin/isolate_holder.cc

Index: gin/isolate_holder.cc
diff --git a/gin/isolate_holder.cc b/gin/isolate_holder.cc
index 2e707359ca70f51778e179a74c26c95060ed52a1..d42607d86ddea5d4c0915509e1b2dc72ca664176 100644
--- a/gin/isolate_holder.cc
+++ b/gin/isolate_holder.cc
@@ -68,6 +68,30 @@ IsolateHolder::IsolateHolder(
 #endif
 }
 
+IsolateHolder::IsolateHolder(intptr_t* reference_table,
+                             v8::StartupData* existing_blob)
+    : snapshot_creator_(
+          new v8::SnapshotCreator(reference_table, existing_blob)),
+      access_mode_(kSingleThread) {
+  v8::ArrayBuffer::Allocator* allocator = g_array_buffer_allocator;
+  CHECK(allocator) << "You need to invoke gin::IsolateHolder::Initialize first";
+  isolate_ = snapshot_creator_->GetIsolate();
+  isolate_data_.reset(
+      new PerIsolateData(isolate_, allocator, access_mode_, nullptr));
+  isolate_memory_dump_provider_.reset(new V8IsolateMemoryDumpProvider(this));
+#if defined(OS_WIN)
+  {
+    void* code_range;
+    size_t size;
+    isolate_->GetCodeRange(&code_range, &size);
+    Debug::CodeRangeCreatedCallback callback =
+        DebugImpl::GetCodeRangeCreatedCallback();
+    if (code_range && size && callback)
+      callback(code_range, size);
+  }
+#endif
+}
+
 IsolateHolder::~IsolateHolder() {
   if (task_observer_.get())
     base::MessageLoop::current()->RemoveTaskObserver(task_observer_.get());