[Bindings] Create and use V8 context snapshots

pdf/pdfium/pdfium_engine.cc

Index: pdf/pdfium/pdfium_engine.cc
diff --git a/pdf/pdfium/pdfium_engine.cc b/pdf/pdfium/pdfium_engine.cc
index 36790be7d350bc210cfa797b87a3a27c58b5f6f6..9ea6ee8d8f884d68f442a923c5cc93ec484a792a 100644
--- a/pdf/pdfium/pdfium_engine.cc
+++ b/pdf/pdfium/pdfium_engine.cc
@@ -597,8 +597,8 @@ void SetUpV8() {
                                  gin::IsolateHolder::kStableV8Extras,
                                  gin::ArrayBufferAllocator::SharedInstance());
   DCHECK(!g_isolate_holder);
-  g_isolate_holder = new gin::IsolateHolder(base::ThreadTaskRunnerHandle::Get(),
-                                            gin::IsolateHolder::kSingleThread);
+  g_isolate_holder =
+      new gin::IsolateHolder(base::ThreadTaskRunnerHandle::Get());
   g_isolate_holder->isolate()->Enter();
 }