Reland: Update FlatBuffers to include multiple improvements.

This CL updates FlatBuffers to the latest version 1.6.x. This is necessary to
include the following changes to the library:
 - d7ac378: Offset<T>::IsNull method.
 - 93c0960: --keep-prefix compiler option.
 - c559eb4: Generate files for empty schemas.
 - aaf5598: Fix path comparison on Windows.
 - fb87c0d: Improve allocator handling (fixes test).
 - 22743ca: Fix --keep-prefix bugs.
 - 642254b: Fix one more --keep-prefix issue.
 - dd05f32: Add tests for nested FlatBuffers.
 - 01c50d5: Get rid of move semantics in VectorIterator.

This is a reland of https://codereview.chromium.org/2883063002/ with a
compile flag added to Windows build suppressing the alignment warning.

BUG=611351,713774
TBR=palmer@chromium.org

Review-Url: https://codereview.chromium.org/2923203002
Cr-Commit-Position: refs/heads/master@{#477947}

DEPS

@@ -226,7 +226,7 @@ deps = {
     Var('chromium_git') + '/chromium/deps/flac.git' + '@' + '7d0f5b3a173ffe98db08057d1f52b7787569e0a6',
 
   'src/third_party/flatbuffers/src':
-    Var('chromium_git') + '/external/github.com/google/flatbuffers.git' + '@' + 'e92ae5199d52fd59540a800bec7eef46cd778257',
+    Var('chromium_git') + '/external/github.com/google/flatbuffers.git' + '@' + '01c50d57a67a52ee3cddd81b54d4647e9123a290',
 
   'src/third_party/pyftpdlib/src':
     Var('chromium_git') + '/external/pyftpdlib.git' + '@' + '2be6d65e31c7ee6320d059f581f05ae8d89d7e45',

third_party/flatbuffers/BUILD.gn

@@ -9,26 +9,45 @@ config("flatbuffers_config") {
   include_dirs = [ "src/include" ]
 }
 
+# The part of FlatBuffers that Chrome is interested in.
 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" ]
 }
 
+# The complete FlatBuffers library, as required to build the flatc compiler and
+# some of the tests.
 source_set("compiler_files") {
+  include_dirs = [ "src/grpc" ]
   sources = [
+    "src/grpc/src/compiler/config.h",
+    "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/flatc.h",
+    "src/include/flatbuffers/flexbuffers.h",
+    "src/include/flatbuffers/grpc.h",
+    "src/include/flatbuffers/hash.h",
     "src/include/flatbuffers/idl.h",
+    "src/include/flatbuffers/reflection.h",
+    "src/include/flatbuffers/reflection_generated.h",
     "src/include/flatbuffers/util.h",
+    "src/src/code_generators.cpp",
+    "src/src/flatc.cpp",
     "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",
@@ -45,7 +64,7 @@ source_set("compiler_files") {
 
 executable("flatc") {
   sources = [
-    "src/src/flatc.cpp",
+    "src/src/flatc_main.cpp",
   ]
   deps = [
     ":compiler_files",
@@ -60,25 +79,18 @@ flatbuffer("flatbuffers_samplebuffer") {
   testonly = true
   sources = [
     # Disabled as workaround for crbug.com/611351
-    # "src/tests/include_test1.fbs",
-    # "src/tests/include_test2.fbs",
+    # "src/tests/include_test/include_test1.fbs",
+    # "src/tests/include_test/sub/include_test2.fbs",
     "src/tests/monster_test.fbs",
     "src/tests/namespace_test/namespace_test1.fbs",
     "src/tests/namespace_test/namespace_test2.fbs",
   ]
+  flatc_include_dirs = [ "src/tests/include_test" ]
 }
 
 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",
-    "src/tests/test.h",
   ]
   deps = [
     ":compiler_files",
@@ -88,4 +100,10 @@ test("flatbuffers_unittest") {
   data = [
     "src/tests/",
   ]
+
+  if (is_win) {
+    # Suppress "object allocated on the heap may not be aligned 16".
+    cflags = [ "/wd4316" ]
+  }
+  defines = [ "FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE" ]
 }

third_party/flatbuffers/README.chromium

 Name: FlatBuffers
 Short Name: flatbuffers
 URL: https://github.com/google/flatbuffers
-Version: e92ae5199d52fd59540a800bec7eef46cd778257
-Date: 2016-06-03
+Version: 01c50d57a67a52ee3cddd81b54d4647e9123a290
+Date: 2017-06-05
 License: Apache 2.0
 License File: LICENSE
 Security Critical: yes

third_party/flatbuffers/flatbuffer.gni

@@ -8,12 +8,23 @@
 #       Specifies the path suffix that output files are generated under. This
 #       path will be appended to root_gen_dir.
 #
-#       Targets that depend on the proto target will be able to include the
-#       resulting flatbuffers header with an include like:
+#       Targets that depend on the flatbuffer target will be able to include
+#       the resulting FlatBuffers header with an include like:
 #         #include "dir/for/my_flatbuffer/buffer_generated.h"
 #       If undefined, this defaults to matchign the input directory for each
 #       .fbs file (you should almost always use the default mode).
 #
+#   flatc_include_dirs (optional)
+#       Specifies the directories which FlatBuffers compiler uses to find
+#       included .fbs files in.
+#
+#       The directories will be tried in the order given, and if all fail (or,
+#       as by default, none are specified) it will try to load relative to the
+#       directory of the schema file being parsed.
+#
+#       TODO(pkalinnikov): Add repository root to this list, to allow including
+#       by absolute path.
+#
 #   deps (optional)
 #       Additional dependencies.
 #
@@ -68,8 +79,18 @@ template("flatbuffer") {
       "$out_dir/{{source_name_part}}_generated.h",
     ]
 
-    args = [
-      "-c",
+    args = [ "-c" ]
+
+    if (defined(invoker.flatc_include_dirs)) {
+      foreach(include_dir, invoker.flatc_include_dirs) {
+        args += [
+          "-I",
+          rebase_path(include_dir, "$root_build_dir"),
+        ]
+      }
+    }
+
+    args += [
       "-o",
       "$out_dir",
       "{{source}}",
@@ -101,7 +122,7 @@ template("flatbuffer") {
     public_configs = [ "//third_party/flatbuffers:flatbuffers_config" ]
 
     public_deps = [
-      # The generated headers reference headers within flatbuffers, so
+      # The generated headers reference headers within FlatBuffers, so
       # dependencies must be able to find those headers too.
       "//third_party/flatbuffers",
     ]