Add BUILD.gn for libflac.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..f8f938d5a51fa9c2918f2b74e5de4409103a45cd
--- /dev/null
+++ b/BUILD.gn
@@ -0,0 +1,83 @@
+# Copyright 2014 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.
+
+config("flac_config") {
+  defines = [
+    "FLAC__NO_DLL",
+  ]
+}
+
+source_set("flac") {
+  sources = [
+    "include/FLAC/all.h",
+    "include/FLAC/assert.h",
+    "include/FLAC/callback.h",
+    "include/FLAC/export.h",
+    "include/FLAC/format.h",
+    "include/FLAC/metadata.h",
+    "include/FLAC/ordinals.h",
+    "include/FLAC/stream_decoder.h",
+    "include/FLAC/stream_encoder.h",
+    "include/share/alloc.h",
+    "src/libFLAC/alloc.c",
+    "src/libFLAC/bitmath.c",
+    "src/libFLAC/bitreader.c",
+    "src/libFLAC/bitwriter.c",
+    "src/libFLAC/cpu.c",
+    "src/libFLAC/crc.c",
+    "src/libFLAC/fixed.c",
+    "src/libFLAC/float.c",
+    "src/libFLAC/format.c",
+    "src/libFLAC/lpc.c",
+    "src/libFLAC/md5.c",
+    "src/libFLAC/memory.c",
+    "src/libFLAC/stream_decoder.c",
+    "src/libFLAC/stream_encoder.c",
+    "src/libFLAC/stream_encoder_framing.c",
+    "src/libFLAC/window.c",
+    "src/libFLAC/include/private/all.h",
+    "src/libFLAC/include/private/bitmath.h",
+    "src/libFLAC/include/private/bitreader.h",
+    "src/libFLAC/include/private/bitwriter.h",
+    "src/libFLAC/include/private/cpu.h",
+    "src/libFLAC/include/private/crc.h",
+    "src/libFLAC/include/private/fixed.h",
+    "src/libFLAC/include/private/float.h",
+    "src/libFLAC/include/private/format.h",
+    "src/libFLAC/include/private/lpc.h",
+    "src/libFLAC/include/private/md5.h",
+    "src/libFLAC/include/private/memory.h",
+    "src/libFLAC/include/private/metadata.h",
+    "src/libFLAC/include/private/stream_encoder_framing.h",
+    "src/libFLAC/include/private/window.h",
+    "src/libFLAC/include/protected/all.h",
+    "src/libFLAC/include/protected/stream_decoder.h",
+    "src/libFLAC/include/protected/stream_encoder.h",
+  ]
+
+  configs -= [ "//build/config/compiler:chromium_code" ]
+  configs += [
+    ":flac_config",
+    "//build/config/compiler:no_chromium_code",
+  ]
+  direct_dependent_configs = [ ":flac_config" ]
+
+  include_dirs = [
+    "include",
+    "src/libFLAC/include",
+  ]
+
+  defines = [
+    "FLAC__OVERFLOW_DETECT",
+    "VERSION=\"1.2.1\"",
+  ]
+
+  if (is_clang) {
+    # libflac converts between FLAC__StreamDecoderState and
+    # FLAC__StreamDecoderInitStatus a lot in stream_decoder.c.
+    cflags = [
+      "-Wno-conversion",
+    ]
+  }
+}