Exclude new file in Google3 build.

public.bzl

Index: public.bzl
diff --git a/public.bzl b/public.bzl
index df3049fdcdff696ada20ab8d414cd0dd02a40c99..7dfecec026d89154fa0ec1d9c7f7a3d3a470afc2 100644
--- a/public.bzl
+++ b/public.bzl
@@ -160,6 +160,7 @@ BASE_SRCS_UNIX = struct(
         "src/ports/SkFontConfigInterface_direct_factory.cpp",
         "src/ports/SkFontMgr_custom_directory_factory.cpp",
         "src/ports/SkFontMgr_custom_embedded_factory.cpp",
+        "src/ports/SkFontMgr_custom_empty_factory.cpp",
         "src/ports/SkFontMgr_empty_factory.cpp",
         "src/ports/SkFontMgr_fontconfig.cpp",
         "src/ports/SkFontMgr_fontconfig_factory.cpp",
@@ -208,6 +209,7 @@ BASE_SRCS_ANDROID = struct(
         "src/ports/SkFontConfigInterface_direct_google3_factory.cpp",
         "src/ports/SkFontMgr_custom_directory_factory.cpp",
         "src/ports/SkFontMgr_custom_embedded_factory.cpp",
+        "src/ports/SkFontMgr_custom_empty_factory.cpp",
         "src/ports/SkFontMgr_empty_factory.cpp",
         "src/ports/SkImageDecoder_empty.cpp",
         "src/ports/SkImageGenerator_none.cpp",
@@ -263,6 +265,7 @@ BASE_SRCS_IOS = struct(
         "src/ports/SkFontConfigInterface_direct_google3_factory.cpp",
         "src/ports/SkFontMgr_custom_directory_factory.cpp",
         "src/ports/SkFontMgr_custom_embedded_factory.cpp",
+        "src/ports/SkFontMgr_custom_empty_factory.cpp",
         "src/ports/SkFontMgr_empty_factory.cpp",
         "src/ports/SkImageGenerator_none.cpp",
         "src/ports/SkTLS_none.cpp",