Able to reproduce the issue and below are the bisect details obtained using per-revision bisect:

You are probably looking for a change made after 481560 (known good), but no later than 481561 (first known bad).
CHANGELOG URL: The script might not always return single CL as suspect as some perf builds might get missing due to failure.

https://chromium.googlesource.com/chromium/src/+log/a95e0bf52bfe99622e4bf498adb761cf9eb218a9..1545ba94087279c773705760d51b728d709fd72d

@dsinclair: Assigning to you, kindly take a look into it Please help us to find an owner if not with respect to your change.

Adding Blocker label, please decrease or remove priority if not the case.

Thanks.!

Bisect shows Skia Paths enabling CL.

Not an RBD since the bug doesn't affects the functionality.

The skia code has been disabled again. Removing release block label.

Dan graciously offered to help create a repro case. He'll assign back to me once he's done.

The following revision refers to this bug:
  https://pdfium.googlesource.com/pdfium/+/08c6651ec45b8cf01e6b6bbe8f57b1052554de94

commit 08c6651ec45b8cf01e6b6bbe8f57b1052554de94
Author: dan sinclair <dsinclair@chromium.org>
Date: Mon Jul 10 16:03:02 2017

Add combo box tests.

These tests pass under normal PDFium bug fail when Skia Paths is
enabled.

Bug:  chromium:736695 
Change-Id: I7e3e789ae25857060dd45940c313f5383c548d2c
Reviewed-on: https://pdfium-review.googlesource.com/7450
Commit-Queue: dsinclair <dsinclair@chromium.org>
Reviewed-by: Cary Clark <caryclark@google.com>

[add] https://crrev.com/08c6651ec45b8cf01e6b6bbe8f57b1052554de94/testing/resources/pixel/bug_736695_1.in
[add] https://crrev.com/08c6651ec45b8cf01e6b6bbe8f57b1052554de94/testing/resources/pixel/bug_736695_4_expected.pdf.0.png
[add] https://crrev.com/08c6651ec45b8cf01e6b6bbe8f57b1052554de94/testing/resources/pixel/bug_736695_2.in
[add] https://crrev.com/08c6651ec45b8cf01e6b6bbe8f57b1052554de94/testing/resources/pixel/bug_736695_2_expected.pdf.0.png
[add] https://crrev.com/08c6651ec45b8cf01e6b6bbe8f57b1052554de94/testing/resources/pixel/bug_736695_2.evt
[add] https://crrev.com/08c6651ec45b8cf01e6b6bbe8f57b1052554de94/testing/resources/pixel/bug_736695_3_expected_mac.pdf.0.png
[add] https://crrev.com/08c6651ec45b8cf01e6b6bbe8f57b1052554de94/testing/resources/pixel/bug_736695_3.evt
[add] https://crrev.com/08c6651ec45b8cf01e6b6bbe8f57b1052554de94/testing/resources/pixel/bug_736695_3_expected.pdf.0.png
[add] https://crrev.com/08c6651ec45b8cf01e6b6bbe8f57b1052554de94/testing/resources/pixel/bug_736695_2_expected_mac.pdf.0.png
[add] https://crrev.com/08c6651ec45b8cf01e6b6bbe8f57b1052554de94/testing/resources/pixel/bug_736695_3.in
[add] https://crrev.com/08c6651ec45b8cf01e6b6bbe8f57b1052554de94/testing/resources/pixel/bug_736695_1_expected.pdf.0.png
[add] https://crrev.com/08c6651ec45b8cf01e6b6bbe8f57b1052554de94/testing/resources/pixel/bug_736695_4.in
[add] https://crrev.com/08c6651ec45b8cf01e6b6bbe8f57b1052554de94/testing/resources/pixel/bug_736695_4.evt

Tests landed with https://pdfium-review.googlesource.com/c/7450

This seems to be a difference caused by the progressive renderer. In pdfium_test we call FPDF_RenderPageBitmap() but Chrome uses the FPDF_RenderPageBitmap_Start(), FPDF_RenderPage_Continue() and FPDF_RenderPage_Close() methods.

Interestingly, if you print the PDF from chrome you see the correct widget, which I believe is because Chrome uses the FPDF_RenderPageBitmap() call to rendering the print preview page.

The following revision refers to this bug:
  https://pdfium.googlesource.com/pdfium/+/aeadad1dfb7e4d3582d63dacd2ecbed71a5dd4ec

commit aeadad1dfb7e4d3582d63dacd2ecbed71a5dd4ec
Author: Dan Sinclair <dsinclair@chromium.org>
Date: Tue Jul 18 21:20:38 2017

Make progressive renderer default for pdfium_test.

When Chrome renders PDF pages it uses the progressive renderer. The one
shot renderer is used to render print preview pages. This CL changes
pdfium_test to use the progressive renderer by default to better match
Chrome. This also adds a --render-oneshot flag which will use the
non-progressive renderer.

Bug:  chromium:736695 
Change-Id: If79333ae10a0ed1c9bce1290caad8d531e6709aa
Reviewed-on: https://pdfium-review.googlesource.com/8130
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>

[modify] https://crrev.com/aeadad1dfb7e4d3582d63dacd2ecbed71a5dd4ec/testing/tools/test_runner.py
[modify] https://crrev.com/aeadad1dfb7e4d3582d63dacd2ecbed71a5dd4ec/samples/pdfium_test.cc
[modify] https://crrev.com/aeadad1dfb7e4d3582d63dacd2ecbed71a5dd4ec/testing/tools/run_corpus_tests.py

Fixed here: https://pdfium-review.googlesource.com/c/8270/