Roll pdfium forward to ae4256f.

DEPS

 # This file is automatically processed to create .DEPS.git which is the file
 # that gclient uses under git.
 #
 # See http://code.google.com/p/chromium/wiki/UsingGit
 #
 # To test manually, run:
 #   python tools/deps2git/deps2git.py -o .DEPS.git -w <gclientdir>
 # where <gcliendir> is the absolute path to the directory containing the
 # .gclient file (the parent of 'src').
 #
 # Then commit .DEPS.git locally (gclient doesn't like dirty trees) and run
 #   gclient sync
 # Verify the thing happened you wanted. Then revert your .DEPS.git change
 # DO NOT CHECK IN CHANGES TO .DEPS.git upstream. It will be automatically
 # updated by a bot when you modify this one.
 #
 # When adding a new dependency, please update the top-level .gitignore file
 # to list the dependency's destination directory.
 
 vars = {
   'chromium_git': 'https://chromium.googlesource.com',
   'skia_revision': '2ced78866fcadd98895777c8dffe92e229775181',
   'v8_revision': '230d131d173ab2d60291d303177bc04ec3f6e519',
   'angle_revision': 'bdd419f9f5b006e913606e7363125942c8ae06bc',
   'buildtools_revision': '565d04e8741429fb1b4f26d102f2c6c3b849edeb',
   'dart_revision': 'cab003366785773ace16b5305ac1f33c228cac54',
   'dart_observatory_packages_revision': 'cdc4b3d4c15b9c0c8e7702dff127b440afbb7485',
-  'pdfium_revision': 'b0115665b0f33971f1b7077740d51e155583cec0',
+  'pdfium_revision': 'ae4256f45df69bbfdf722a6ec17e1e851911ae4e',
   'boringssl_revision': '642f1498d056dbba3e50ed5a232ab2f482626dec',
   'lss_revision': '6f97298fe3794e92c8c896a6bc06e0b36e4c3de3',
   'nss_revision': 'bb4e75a43d007518ae7d618665ea2f25b0c60b63',
   'nacl_revision': '8071f876e10f96da879853a7705d9c5aba378839',
   'archive_dart_revision': '07ffd98c5403b7f9ae067b57dc9487611be420f5',
   'args_dart_revision': 'e0e8377412ee6cd6a5a4a8632848181c1db91f44',
   'box2d_dart_revision': 'c5e65d9546275e78ad2a1d51b459e7638f6e4323',
   'cassowary_dart_revision': '7e5afc5b3956a18636d5b37b1dcba1705865564b',
   'collection_dart_revision': '79ebc6fc2dae581cb23ad50a5c600c1b7dd132f8',
   'crypto_dart_revision': 'd4558dea1639e5ad2a41d045265b8ece270c2d90',
@@ skipping 391 matching lines @@
     'name': 'prediction_resources',
     'pattern': '',
     'action': [ 'download_from_google_storage',
                 '--no_resume',
                 '--no_auth',
                 '--bucket', 'mojo/prediction',
                 '-d', 'src/services/prediction/res',
     ],
   },
 ]