The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4d87bccef0d6c07cdecf43449af4157736ac3f35

commit 4d87bccef0d6c07cdecf43449af4157736ac3f35
Author: Dominic Mazzoni <dmazzoni@chromium.org>
Date: Tue Mar 13 18:38:06 2018

Expose selection in the PDF accessibility tree

Bug:  816529 
Tbr: tsepez@chromium.org
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_mojo
Change-Id: I89646a49d23a5591b5f564412450832893bb3cb3
Reviewed-on: https://chromium-review.googlesource.com/936454
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Raymes Khoury <raymes@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Katie Dektar <katie@chromium.org>
Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#542867}
[modify] https://crrev.com/4d87bccef0d6c07cdecf43449af4157736ac3f35/chrome/browser/pdf/pdf_extension_test.cc
[modify] https://crrev.com/4d87bccef0d6c07cdecf43449af4157736ac3f35/components/pdf/renderer/pdf_accessibility_tree.cc
[modify] https://crrev.com/4d87bccef0d6c07cdecf43449af4157736ac3f35/components/pdf/renderer/pdf_accessibility_tree.h
[modify] https://crrev.com/4d87bccef0d6c07cdecf43449af4157736ac3f35/content/renderer/accessibility/render_accessibility_impl.cc
[modify] https://crrev.com/4d87bccef0d6c07cdecf43449af4157736ac3f35/pdf/out_of_process_instance.cc
[modify] https://crrev.com/4d87bccef0d6c07cdecf43449af4157736ac3f35/pdf/pdf_engine.h
[modify] https://crrev.com/4d87bccef0d6c07cdecf43449af4157736ac3f35/pdf/pdfium/pdfium_engine.cc
[modify] https://crrev.com/4d87bccef0d6c07cdecf43449af4157736ac3f35/pdf/pdfium/pdfium_engine.h
[modify] https://crrev.com/4d87bccef0d6c07cdecf43449af4157736ac3f35/ppapi/c/private/ppb_pdf.h
[modify] https://crrev.com/4d87bccef0d6c07cdecf43449af4157736ac3f35/ppapi/proxy/ppapi_messages.h
[modify] https://crrev.com/4d87bccef0d6c07cdecf43449af4157736ac3f35/ui/accessibility/ax_tree_serializer.h