Roll pdfium, add GN build for pdf and pdfium.

build/config/compiler/BUILD.gn

 # Copyright (c) 2013 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/android/config.gni")
 if (cpu_arch == "arm") {
   import("//build/config/arm.gni")
 }
 if (is_posix) {
   import("//build/config/gcc/gcc_version.gni")
@@ skipping 40 matching lines @@
                   # structured exceptions (only C++ ones).
       ]
     }
   } else {
     # Common GCC compiler flags setup.
     # --------------------------------
     cflags += [
       "-fno-strict-aliasing",  # See http://crbug.com/32204
     ]
     cflags_cc += [
-      "-fno-exceptions",
       "-fno-threadsafe-statics",
       # Not exporting C++ inline functions can generally be applied anywhere
       # so we do so here. Normal function visibility is controlled by
       # //build/config/gcc:symbol_visibility_hidden.
       "-fvisibility-inlines-hidden",
     ]
 
     # Stack protection.
     if (is_mac) {
       cflags += [ "-fstack-protector-all" ]
@@ skipping 721 matching lines @@
   } else {
     cflags = [ "-g1" ]
   }
 }
 
 config("no_symbols") {
   if (!is_win) {
     cflags = [ "-g0" ]
   }
 }