[Bindings] Create and use V8 context snapshots

pdf/pdfium/pdfium_engine.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "pdf/pdfium/pdfium_engine.h"
 
 #include <math.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 579 matching lines @@
   return base::UTF16ToUTF8(value);
 }
 
 gin::IsolateHolder* g_isolate_holder = nullptr;
 
 void SetUpV8() {
   gin::IsolateHolder::Initialize(gin::IsolateHolder::kNonStrictMode,
                                  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());

[Yuki, 2017/06/20 14:20:10]

Is this a good change?  It seems better to explicitly pass kSingleThread rather
than implicitly assuming kSingleThread.

[peria, 2017/06/21 07:19:15]

Done.

   g_isolate_holder->isolate()->Enter();
 }
 
 void TearDownV8() {
   g_isolate_holder->isolate()->Exit();
   delete g_isolate_holder;
   g_isolate_holder = nullptr;
 }
 
 int GetBlockForJpeg(void* param,
@@ skipping 3526 matching lines @@
   FPDF_DOCUMENT doc =
       FPDF_LoadMemDocument(pdf_buffer, pdf_buffer_size, nullptr);
   if (!doc)
     return false;
   bool success = FPDF_GetPageSizeByIndex(doc, page_number, width, height) != 0;
   FPDF_CloseDocument(doc);
   return success;
 }
 
 }  // namespace chrome_pdf