Add missing header files to GN files

ppapi/thunk/BUILD.gn

Index: ppapi/thunk/BUILD.gn
diff --git a/ppapi/thunk/BUILD.gn b/ppapi/thunk/BUILD.gn
index 258e04464946c1b5c50ae150441bdc4b53d2424f..913748f44a73102deaa37928a7e348ea66d96d32 100644
--- a/ppapi/thunk/BUILD.gn
+++ b/ppapi/thunk/BUILD.gn
@@ -12,6 +12,16 @@ source_set("thunk") {
   sources = [
     "enter.cc",
     "enter.h",
+    "interfaces_legacy.h",
+    "interfaces_postamble.h",
+    "interfaces_ppb_private.h",
+    "interfaces_ppb_private_flash.h",
+    "interfaces_ppb_private_no_permissions.h",
+    "interfaces_ppb_public_dev.h",
+    "interfaces_ppb_public_dev_channel.h",
+    "interfaces_ppb_public_stable.h",
+    "interfaces_preamble.h",
+    "ppapi_thunk_export.h",
     "ppb_audio_api.h",
     "ppb_audio_buffer_api.h",
     "ppb_audio_buffer_thunk.cc",
@@ -22,6 +32,7 @@ source_set("thunk") {
     "ppb_audio_input_api.h",
     "ppb_audio_thunk.cc",
     "ppb_broker_api.h",
+    "ppb_browser_font_singleton_api.h",
     "ppb_browser_font_trusted_api.h",
     "ppb_buffer_api.h",
     "ppb_camera_capabilities_api.h",
@@ -50,6 +61,7 @@ source_set("thunk") {
     "ppb_find_private_thunk.cc",
     "ppb_flash_clipboard_api.h",
     "ppb_flash_drm_api.h",
+    "ppb_flash_file_api.h",
     "ppb_flash_font_file_api.h",
     "ppb_flash_fullscreen_api.h",
     "ppb_flash_functions_api.h",
@@ -144,6 +156,7 @@ source_set("thunk") {
     "ppb_websocket_thunk.cc",
     "ppb_x509_certificate_private_api.h",
     "ppb_x509_certificate_private_thunk.cc",
+    "resource_creation_api.h",
     "thunk.h",
   ]