It has a CL to roll new pdfium, so probably it has some changes affect the test.
I'm going to disable the test tentatively.

cc'ed to thestig as an OWNER of PDF.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/bced9d289b945b1b5cb6ffcec48d09bc150b6347

commit bced9d289b945b1b5cb6ffcec48d09bc150b6347
Author: Makoto Shimazu <shimazu@chromium.org>
Date: Mon Dec 17 01:50:00 2018

Disable flaky test on ASan/LSan: PDFExtensionTest.Elements

TBR: thestig@chromium.org
NOTRY: true
Bug:  915555 
Change-Id: Iedd08ea490fd484b0e83434c0f969d10169e7fea
Reviewed-on: https://chromium-review.googlesource.com/c/1379591
Reviewed-by: Makoto Shimazu <shimazu@chromium.org>
Commit-Queue: Makoto Shimazu <shimazu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#617035}
[modify] https://crrev.com/bced9d289b945b1b5cb6ffcec48d09bc150b6347/chrome/browser/pdf/pdf_extension_test.cc

 Issue 915504  has been merged into this issue.

FYI; findit said https://chromium.googlesource.com/chromium/src/+/609997fe600b963b4830c2a713be6839f1856209 may be a culprit.

https://findit-for-me.appspot.com/waterfall/flake/flake-culprit?key=ag9zfmZpbmRpdC1mb3ItbWVyQwsSDEZsYWtlQ3VscHJpdCIxY2hyb21pdW0vNjA5OTk3ZmU2MDBiOTYzYjQ4MzBjMmE3MTNiZTY4MzlmMTg1NjIwOQw

Removed sheriff flag since it's disabled.

The crash is not in PDF code, but rather in cc/ code.

[1:8:1216/092421.737120:FATAL:async_layer_tree_frame_sink.cc(309)] Check failed: pipeline_reporting_frame_times_.size() <= 25u (26 vs. 25)
    #0 0x5602708b5761 in __interceptor_backtrace /b/swarming/w/ir/kitchen-workdir/src/third_party/llvm/compiler-rt/lib/asan/../sanitizer_common/sanitizer_common_interceptors.inc:4041:13
    #1 0x560282703e5f in base::debug::StackTrace::StackTrace(unsigned long) ./../../base/debug/stack_trace_posix.cc:820:41
    #2 0x560282495170 in logging::LogMessage::~LogMessage() ./../../base/logging.cc:592:29
    #3 0x560289c2682a in cc::mojo_embedder::AsyncLayerTreeFrameSink::OnBeginFrame(viz::BeginFrameArgs const&, base::flat_map<unsigned int, gfx::PresentationFeedback, std::__1::less<void> > const&) ./../../cc/mojo_embedder/async_layer_tree_frame_sink.cc:309:3
    #4 0x560279afcb1e in viz::mojom::CompositorFrameSinkClientStubDispatch::Accept(viz::mojom::CompositorFrameSinkClient*, mojo::Message*) ./gen/services/viz/public/interfaces/compositing/compositor_frame_sink.mojom.cc:1392:13

PDFExtensionTest.Elements and PDFExtensionTest.ToolbarManager are currently the most and third-most flaky browser tests according to the flakiness dashboard. Both fail on LSAN/ASAN and linux-chromeos-dbg.

I am making sure that the tests are disabled.

yiyix@ PTAL

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5a36d4270ea3dd774c7164f49909cac9adc4f270

commit 5a36d4270ea3dd774c7164f49909cac9adc4f270
Author: Dominic Battre <battre@chromium.org>
Date: Mon Jan 14 16:41:04 2019

Disable PDFExtensionTest.Elements and .ToolbarManager

See bug for details.

TBR=yiyix@chromium.org,thestig@chromium.org

Bug:  915555 
Change-Id: I39ba46a6c72cfcd35bd73ac082d56795a69976f0
Reviewed-on: https://chromium-review.googlesource.com/c/1409547
Reviewed-by: Dominic Battré <battre@chromium.org>
Commit-Queue: Dominic Battré <battre@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622473}
[modify] https://crrev.com/5a36d4270ea3dd774c7164f49909cac9adc4f270/chrome/browser/pdf/pdf_extension_test.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d43269d116df528e1d87783589e075b8387bdc00

commit d43269d116df528e1d87783589e075b8387bdc00
Author: Sadrul Chowdhury <sadrul@chromium.org>
Date: Tue Jan 15 04:24:09 2019

Revert "Disable PDFExtensionTest.Elements and .ToolbarManager"

This reverts commit 5a36d4270ea3dd774c7164f49909cac9adc4f270.

Reason for revert: crrev.com/622484 should fix the test.

Original change's description:
> Disable PDFExtensionTest.Elements and .ToolbarManager
> 
> See bug for details.
> 
> TBR=yiyix@chromium.org,thestig@chromium.org
> 
> Bug:  915555 
> Change-Id: I39ba46a6c72cfcd35bd73ac082d56795a69976f0
> Reviewed-on: https://chromium-review.googlesource.com/c/1409547
> Reviewed-by: Dominic Battré <battre@chromium.org>
> Commit-Queue: Dominic Battré <battre@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#622473}

TBR=thestig@chromium.org,battre@chromium.org,yiyix@chromium.org

Bug:  915555 
Change-Id: Ia43b1c06d9165e19cd0d0832e9b7148ecb96f85e
Reviewed-on: https://chromium-review.googlesource.com/c/1410391
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Commit-Queue: Sadrul Chowdhury <sadrul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622728}
[modify] https://crrev.com/d43269d116df528e1d87783589e075b8387bdc00/chrome/browser/pdf/pdf_extension_test.cc