Add files for libexif GN target.

third_party/libexif/BUILD.gn

Index: third_party/libexif/BUILD.gn
diff --git a/third_party/libexif/BUILD.gn b/third_party/libexif/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..98d11f6586f18408b5dfb8582d7967083ef896f6
--- /dev/null
+++ b/third_party/libexif/BUILD.gn
@@ -0,0 +1,67 @@
+# Copyright 2015 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.
+
+# Linux should use system libexif
+if (!is_linux || is_chromeos) {
+
+  # TODO(GYP) Add Linux support, if neccessary.

[Lei Zhang, 2015/01/15 08:30:27]

... that is, you can put my username here. I'll take care of it. BTW, there's a
typo: "necessary"

[Slava Chigrin, 2015/01/15 08:42:48]

Done.

+  config("libexif_config") {
+    include_dirs = [ "sources" ]
+  }
+
+  static_library("libexif") {
+    sources = [
+      "sources/libexif/exif-byte-order.c",
+      "sources/libexif/exif-content.c",
+      "sources/libexif/exif-data.c",
+      "sources/libexif/exif-entry.c",
+      "sources/libexif/exif-format.c",
+      "sources/libexif/exif-ifd.c",
+      "sources/libexif/exif-loader.c",
+      "sources/libexif/exif-log.c",
+      "sources/libexif/exif-mem.c",
+      "sources/libexif/exif-mnote-data.c",
+      "sources/libexif/exif-tag.c",
+      "sources/libexif/exif-utils.c",
+      "sources/libexif/canon/exif-mnote-data-canon.c",
+      "sources/libexif/canon/mnote-canon-entry.c",
+      "sources/libexif/canon/mnote-canon-tag.c",
+      "sources/libexif/fuji/exif-mnote-data-fuji.c",
+      "sources/libexif/fuji/mnote-fuji-entry.c",
+      "sources/libexif/fuji/mnote-fuji-tag.c",
+      "sources/libexif/olympus/exif-mnote-data-olympus.c",
+      "sources/libexif/olympus/mnote-olympus-entry.c",
+      "sources/libexif/olympus/mnote-olympus-tag.c",
+      "sources/libexif/pentax/exif-mnote-data-pentax.c",
+      "sources/libexif/pentax/mnote-pentax-entry.c",
+      "sources/libexif/pentax/mnote-pentax-tag.c",
+    ]
+
+    include_dirs = [ "sources" ]
+
+    #TODO(GYP): Additional options for non-Windows platforms.

[Lei Zhang, 2015/01/15 08:30:26]

nit: space after the '#', ditto below.

[Slava Chigrin, 2015/01/15 08:42:48]

Done.

+
+    if (is_win) {
+      defines = [
+        # This seems like a hack, but this is what WebKit Win does.
+        "snprintf=_snprintf",
+        "inline=__inline",
+      ]
+
+      ldflags = [ "/DEF:" + rebase_path("libexif.def") ]
+
+      cflags = [
+        "/wd4018",  # size/unsigned mismatch
+        "/wd4267",  # size_t -> ExifLong truncation on amd64
+      ]
+
+      #TODO(GYP): Remove /analyze, when it will be used in GN.

[Lei Zhang, 2015/01/15 08:24:11]

Remove -> Add?

[Slava Chigrin, 2015/01/15 08:42:48]

In GYP this switch in "AdditionalOptions!" (note exclamation mark)  list. And
also comment before says "...Therefore, /analyze is disabled for this
project...."
thats why I thought that this compiler option is being removed there.

Thats why I decided to change comment to more neutral "handle" word, to avoid
confusion. If I something misunderstood, I can change it to "Add", as you asked.

[Lei Zhang, 2015/01/15 08:46:07]

Right, sorry for the confusion. It's getting late here...

+    }
+
+    configs -= [ "//build/config/compiler:chromium_code" ]
+    configs += [ "//build/config/compiler:no_chromium_code" ]
+
+    public_configs = [ ":libexif_config" ]
+  }
+}