Run V8 in predictable mode for pdfium_test

testing/embedder_test.cpp

 // Copyright (c) 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 "embedder_test.h"
 
 #include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ skipping 175 matching lines @@
   default_delegate_ = new EmbedderTestDefaultDelegate();
   delegate_ = default_delegate_;
 }
 
 EmbedderTest::~EmbedderTest() {
   delete default_delegate_;
 }
 
 void EmbedderTest::SetUp() {
     v8::V8::InitializeICU();
+    // By enabling predicatble mode, V8 won't post any background tasks.
+    const char predictable_flag[] = "--predictable";
+    v8::V8::SetFlagsFromString(predictable_flag, strlen(predictable_flag));
 
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
     ASSERT_TRUE(GetExternalData(g_exe_path_, "natives_blob.bin", &natives_));
     ASSERT_TRUE(GetExternalData(g_exe_path_, "snapshot_blob.bin", &snapshot_));
     v8::V8::SetNativesDataBlob(&natives_);
     v8::V8::SetSnapshotDataBlob(&snapshot_);
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA
 
     FPDF_InitLibrary();
 
@@ skipping 125 matching lines @@
 }
 
 // Can't use gtest-provided main since we need to stash the path to the
 // executable in order to find the external V8 binary data files.
 int main(int argc, char** argv) {
   g_exe_path_ = argv[0];
   testing::InitGoogleTest(&argc, argv);
   testing::InitGoogleMock(&argc, argv);
   return RUN_ALL_TESTS();
 }