Simplify TestFontMapper

TestFontMapper mainly exists to expose CFX_FontMapper's private methods
to unit tests. Instead of manually defining pass-through methods to call
CFX_FontMapper methods, switch to using-statements.

Change-Id: I46925c82eea04d474515d70c23e92bce8caee9f4
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/135870
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
diff --git a/core/fxge/cfx_fontmapper_unittest.cpp b/core/fxge/cfx_fontmapper_unittest.cpp
index 31b35eb..6acc7d3 100644
--- a/core/fxge/cfx_fontmapper_unittest.cpp
+++ b/core/fxge/cfx_fontmapper_unittest.cpp
@@ -47,20 +47,8 @@
  public:
   TestFontMapper() : CFX_FontMapper(CFX_GEModule::Get()->GetFontMgr()) {}
 
-  RetainPtr<CFX_Face> GetCachedTTCFace(void* font_handle,
-                                       size_t ttc_size,
-                                       size_t data_size) {
-    return CFX_FontMapper::GetCachedTTCFace(font_handle, ttc_size, data_size);
-  }
-
-  RetainPtr<CFX_Face> GetCachedFace(void* font_handle,
-                                    ByteString subst_name,
-                                    int weight,
-                                    bool is_italic,
-                                    size_t data_size) {
-    return CFX_FontMapper::GetCachedFace(font_handle, subst_name, weight,
-                                         is_italic, data_size);
-  }
+  using CFX_FontMapper::GetCachedFace;
+  using CFX_FontMapper::GetCachedTTCFace;
 };
 
 class CFXFontMapperSystemFontInfoTest : public testing::Test {