Update FlatBuffers to version 1.5.0.

third_party/flatbuffers/BUILD.gn

 # Copyright 2016 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.
 
 import("//testing/test.gni")
 import("//third_party/flatbuffers/flatbuffer.gni")
 
 config("flatbuffers_config") {
   include_dirs = [ "src/include" ]
+
+  # This is to fix crbug.com/699958.
+  defines = [ "FLATBUFFERS_CPP98_STL" ]
 }
 
 source_set("flatbuffers") {
   sources = [
     "src/include/flatbuffers/flatbuffers.h",
     "src/include/flatbuffers/hash.h",
   ]
 
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
   public_configs = [ ":flatbuffers_config" ]
 }
 
 source_set("compiler_files") {
+  include_dirs = [ "src/grpc" ]
   sources = [
+    "src/grpc/src/compiler/cpp_generator.cc",
+    "src/grpc/src/compiler/cpp_generator.h",
+    "src/grpc/src/compiler/go_generator.cc",
+    "src/grpc/src/compiler/go_generator.h",
+    "src/grpc/src/compiler/schema_interface.h",
     "src/include/flatbuffers/code_generators.h",
     "src/include/flatbuffers/idl.h",
     "src/include/flatbuffers/util.h",
     "src/src/idl_gen_cpp.cpp",
     "src/src/idl_gen_fbs.cpp",
     "src/src/idl_gen_general.cpp",
     "src/src/idl_gen_go.cpp",
+    "src/src/idl_gen_grpc.cpp",
     "src/src/idl_gen_js.cpp",
     "src/src/idl_gen_php.cpp",
     "src/src/idl_gen_python.cpp",
     "src/src/idl_gen_text.cpp",
     "src/src/idl_parser.cpp",
     "src/src/reflection.cpp",
     "src/src/util.cpp",
   ]
   visibility = [ ":*" ]
   deps = [
@@ skipping 29 matching lines @@
 test("flatbuffers_unittest") {
   sources = [
     # The following files are not included in :flatbuffers
     # but are listed here because test.cpp tests more than what will
     # get included into Chrome (reflection and generation).
     "src/include/reflection.h",
     "src/include/reflection_generated.h",
 
     # This is the actual test.
     "src/tests/test.cpp",
+
+    # TODO(pkalinnikov): Add "grpc/tests/grpctest.cpp" as well.

[engedy, 2017/03/09 17:39:32]

nit: Could you please reference https://crbug.com/NNNNNN here?

   ]
   deps = [
     ":compiler_files",
     ":flatbuffers",
     ":flatbuffers_samplebuffer",
   ]
   data = [
     "src/tests/",
   ]
+  defines = [ "FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE" ]
 }