Fix V8 isolate setup in embedder tests and roll V8 to 055bfa7.

testing/js_embedder_test.cpp

 // Copyright 2015 PDFium 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 "testing/js_embedder_test.h"
 
 JSEmbedderTest::JSEmbedderTest()
-    : m_pArrayBufferAllocator(new FXJS_ArrayBufferAllocator) {
+    : m_pArrayBufferAllocator(new FXJS_ArrayBufferAllocator),
+      m_pIsolate(nullptr) {}
+
+JSEmbedderTest::~JSEmbedderTest() {}
+
+void JSEmbedderTest::SetUp() {
   v8::Isolate::CreateParams params;
   params.array_buffer_allocator = m_pArrayBufferAllocator.get();
   m_pIsolate = v8::Isolate::New(params);
-}
 
-JSEmbedderTest::~JSEmbedderTest() {
-  m_pIsolate->Dispose();
-}
-
-void JSEmbedderTest::SetUp() {
   EmbedderTest::SetExternalIsolate(m_pIsolate);
   EmbedderTest::SetUp();
 
   v8::Isolate::Scope isolate_scope(m_pIsolate);
 #ifdef PDF_ENABLE_XFA
   v8::Locker locker(m_pIsolate);
 #endif  // PDF_ENABLE_XFA
   v8::HandleScope handle_scope(m_pIsolate);
   FXJS_PerIsolateData::SetUp(m_pIsolate);
   FXJS_InitializeRuntime(m_pIsolate, nullptr, &m_pPersistentContext,
                          &m_StaticObjects);
 }
 
 void JSEmbedderTest::TearDown() {
   FXJS_ReleaseRuntime(m_pIsolate, &m_pPersistentContext, &m_StaticObjects);
   m_pPersistentContext.Reset();
   FXJS_Release();
   EmbedderTest::TearDown();
+  m_pIsolate->Dispose();
+  m_pIsolate = nullptr;
 }
 
 v8::Isolate* JSEmbedderTest::isolate() {
   return m_pIsolate;
 }
 
 v8::Local<v8::Context> JSEmbedderTest::GetV8Context() {
   return m_pPersistentContext.Get(m_pIsolate);
 }