Revert the following commit (to support bad-font-gc2.patch):

commit d4806d20fda56e9bac259fddf10b7439ce749add
Author: Hao Liu <haoliuk@chromium.org>
Date:   Mon Mar 18 22:56:31 2024 +0000

    Cleanup leftover non-used custom_font_data methods
    
    This is to clean up non-used custom_font_data methods. Their usage has
    been deleted in a previous CL.
    https://chromium-review.googlesource.com/c/chromium/src/+/5262982/29/third_party/blink/renderer/core/css/css_font_face_source.cc#b95
    
    Change-Id: I90c3ae794a6caf71526c81a56795e95c23cc3fb5
    Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5368244
    Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
    Commit-Queue: Ian Kilpatrick <ikilpatrick@chromium.org>
    Cr-Commit-Position: refs/heads/main@{#1274525}

--- a/third_party/blink/renderer/core/css/css_custom_font_data.h
+++ b/third_party/blink/renderer/core/css/css_custom_font_data.h
@@ -55,6 +55,7 @@ class CSSCustomFontData final : public C
 
   bool IsLoading() const override { return is_loading_; }
   bool IsLoadingFallback() const override { return true; }
+  void ClearFontFaceSource() override { font_face_source_ = nullptr; }
 
   bool IsPendingDataUrl() const override {
     return font_face_source_ && font_face_source_->IsPendingDataUrl();
--- a/third_party/blink/renderer/platform/fonts/custom_font_data.h
+++ b/third_party/blink/renderer/platform/fonts/custom_font_data.h
@@ -46,6 +46,7 @@ class PLATFORM_EXPORT CustomFontData : p
   virtual bool IsLoading() const { return false; }
   virtual bool IsLoadingFallback() const { return false; }
   virtual bool ShouldSkipDrawing() const { return false; }
+  virtual void ClearFontFaceSource() {}
   virtual bool IsPendingDataUrl() const { return false; }
 
  protected: