Add string pools to save storage.

BUILD.gn

 # Copyright 2016 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_overrides/v8.gni")
 import("//testing/test.gni")
 import("pdfium.gni")
 
 config("pdfium_common_config") {
   cflags = []
@@ skipping 691 matching lines @@
     "core/fxcrt/fx_xml_composer.cpp",
     "core/fxcrt/fx_xml_parser.cpp",
     "core/fxcrt/fxcrt_posix.cpp",
     "core/fxcrt/fxcrt_posix.h",
     "core/fxcrt/fxcrt_stream.cpp",
     "core/fxcrt/fxcrt_windows.cpp",
     "core/fxcrt/fxcrt_windows.h",
     "core/fxcrt/include/cfx_count_ref.h",
     "core/fxcrt/include/cfx_observable.h",
     "core/fxcrt/include/cfx_retain_ptr.h",
+    "core/fxcrt/include/cfx_string_pool_template.h",
     "core/fxcrt/include/fx_basic.h",
     "core/fxcrt/include/fx_coordinates.h",
     "core/fxcrt/include/fx_ext.h",
     "core/fxcrt/include/fx_memory.h",
     "core/fxcrt/include/fx_safe_types.h",
     "core/fxcrt/include/fx_stream.h",
     "core/fxcrt/include/fx_string.h",
     "core/fxcrt/include/fx_system.h",
     "core/fxcrt/include/fx_ucd.h",
     "core/fxcrt/include/fx_xml.h",
@@ skipping 925 matching lines @@
     "core/fpdfapi/fpdf_parser/cpdf_syntax_parser_unittest.cpp",
     "core/fpdfapi/fpdf_parser/fpdf_parser_decode_unittest.cpp",
     "core/fpdfdoc/cpdf_filespec_unittest.cpp",
     "core/fpdfdoc/cpdf_formfield_unittest.cpp",
     "core/fpdftext/fpdf_text_int_unittest.cpp",
     "core/fxcodec/codec/fx_codec_jpx_unittest.cpp",
     "core/fxcodec/jbig2/JBig2_Image_unittest.cpp",
     "core/fxcrt/cfx_count_ref_unittest.cpp",
     "core/fxcrt/cfx_observable_unittest.cpp",
     "core/fxcrt/cfx_retain_ptr_unittest.cpp",
+    "core/fxcrt/cfx_string_pool_template_unittest.cpp",
     "core/fxcrt/fx_basic_bstring_unittest.cpp",
     "core/fxcrt/fx_basic_gcc_unittest.cpp",
     "core/fxcrt/fx_basic_memmgr_unittest.cpp",
     "core/fxcrt/fx_basic_util_unittest.cpp",
     "core/fxcrt/fx_basic_wstring_unittest.cpp",
     "core/fxcrt/fx_bidi_unittest.cpp",
     "core/fxcrt/fx_extension_unittest.cpp",
     "core/fxcrt/fx_system_unittest.cpp",
     "core/fxge/dib/fx_dib_engine_unittest.cpp",
     "fpdfsdk/fpdfdoc_unittest.cpp",
@@ skipping 87 matching lines @@
 }
 
 if (pdf_is_standalone) {
   source_set("samples") {
     testonly = true
     deps = [
       "//samples",
     ]
   }
 }