Add v8_platform to the JS dependencies in the GN build.

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.
 
 pdf_use_skia = false
 
 config("pdfium_config") {
   cflags = []
   defines = [
     "FOXIT_CHROME_BUILD",
@@ skipping 790 matching lines @@
   if (is_posix) {
     configs -= [ "//build/config/gcc:no_exceptions" ]
   }
   configs += [ ":pdfium_config", "//build/config/compiler:no_chromium_code" ]
   include_dirs = [
     "//v8",
     "//v8/include",
   ]
   deps = [
     "//v8",
+    "//v8:v8_libplatform",
   ]
   forward_dependent_configs_from = [ "//v8" ]
 }
 
 static_library("jsapi") {
   sources = [
     "fpdfsdk/include/jsapi/fxjs_v8.h",
     "fpdfsdk/src/jsapi/fxjs_v8.cpp",
   ]
 
@@ skipping 37 matching lines @@
     "fpdfsdk/src/formfiller/FFL_RadioButton.cpp",
     "fpdfsdk/src/formfiller/FFL_TextField.cpp",
     "fpdfsdk/src/formfiller/FFL_Utils.cpp",
   ]
   configs -= [ "//build/config/compiler:chromium_code" ]
   if (is_posix) {
     configs -= [ "//build/config/gcc:no_exceptions" ]
   }
   configs += [ ":pdfium_config", "//build/config/compiler:no_chromium_code" ]
 }