Add iterators and unit tests for CPDF_Array class

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_config") {
   cflags = []
@@ skipping 1620 matching lines @@
     ]
   }
 }
 
 test("pdfium_unittests") {
   sources = [
     "core/fpdfapi/fpdf_font/fpdf_font_cid_unittest.cpp",
     "core/fpdfapi/fpdf_font/fpdf_font_unittest.cpp",
     "core/fpdfapi/fpdf_page/fpdf_page_parser_old_unittest.cpp",
     "core/fpdfapi/fpdf_page/fpdf_page_parser_unittest.cpp",
+    "core/fpdfapi/fpdf_parser/cpdf_array_unittest.cpp",
     "core/fpdfapi/fpdf_parser/cpdf_object_unittest.cpp",
     "core/fpdfapi/fpdf_parser/cpdf_parser_unittest.cpp",
     "core/fpdfapi/fpdf_parser/cpdf_simple_parser_unittest.cpp",
     "core/fpdfapi/fpdf_parser/cpdf_syntax_parser_unittest.cpp",
     "core/fpdfapi/fpdf_parser/fpdf_parser_decode_unittest.cpp",
     "core/fpdfdoc/doc_basic_unittest.cpp",
     "core/fpdftext/fpdf_text_int_unittest.cpp",
     "core/fxcodec/codec/fx_codec_jpx_unittest.cpp",
     "core/fxcrt/cfx_retain_ptr_unittest.cpp",
     "core/fxcrt/fx_basic_bstring_unittest.cpp",
@@ skipping 72 matching lines @@
       "//v8:v8_libplatform",
     ]
     include_dirs += [
       "//v8",
       "//v8/include",
     ]
     configs += [ "//v8:external_startup_data" ]
   }
   configs += [ ":pdfium_config" ]
 }