Revert of Add PDFium build_overrides

pdf/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/features.gni")
-import("//build_overrides/pdfium.gni")
+import("//third_party/pdfium/pdfium.gni")
 
 assert(enable_pdf)
 
 pdf_engine = 0  # 0 PDFium
 
 static_library("pdf") {
   deps = [
     "//base",
     "//gin",
     "//net",
@@ skipping 44 matching lines @@
       "pdfium/pdfium_page.h",
       "pdfium/pdfium_range.cc",
       "pdfium/pdfium_range.h",
     ]
   }
 
   if (pdf_enable_xfa) {
     defines = [ "PDF_ENABLE_XFA" ]
   }
 }