You are probably looking for a change made after 371971 (known good), but no later than 371983 (first known bad).
CHANGELOG URL:
https://chromium.googlesource.com/chromium/src/+log/e0eec37304a55f38b31e4c6693fb274eb7ffeea3..fc4981181cc7cf38c573804f3c91271f7b8c900a

I think this is: https://chromium.googlesource.com/chromium/src/+/6b616c49773e7b878799342251519195f3b32067

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/eb3bc319810c236e1a030d0f0c04867e1cdb8862

commit eb3bc319810c236e1a030d0f0c04867e1cdb8862
Author: wangxianzhu <wangxianzhu@chromium.org>
Date: Sat Apr 09 00:53:50 2016

Update PaintLayer::needsPaintPhaseXXX flags when add/remove layer on style change

When addding/removing a layer on style change, we may not
do paint invalidation to update the needsPaintPhaseXXX flags, so
we need to update the flags manually.

In the future, the logic can be simplified by updating the flags
during pre-painting tree walk.

BUG= 598978 

Review URL: https://codereview.chromium.org/1862313002

Cr-Commit-Position: refs/heads/master@{#386264}

[modify] https://crrev.com/eb3bc319810c236e1a030d0f0c04867e1cdb8862/third_party/WebKit/Source/core/layout/LayoutBoxModelObject.cpp
[modify] https://crrev.com/eb3bc319810c236e1a030d0f0c04867e1cdb8862/third_party/WebKit/Source/core/layout/LayoutObject.cpp
[modify] https://crrev.com/eb3bc319810c236e1a030d0f0c04867e1cdb8862/third_party/WebKit/Source/core/paint/PaintLayer.cpp
[modify] https://crrev.com/eb3bc319810c236e1a030d0f0c04867e1cdb8862/third_party/WebKit/Source/core/paint/PaintLayer.h
[modify] https://crrev.com/eb3bc319810c236e1a030d0f0c04867e1cdb8862/third_party/WebKit/Source/core/paint/PaintLayerPainterTest.cpp
[modify] https://crrev.com/eb3bc319810c236e1a030d0f0c04867e1cdb8862/third_party/WebKit/Source/core/paint/README.md

[Automated comment] Less than 2 weeks to go before stable on M50, manual review required.

wangxianzhu@ confirmed it's baked and verified in canary. Merge approved for M50 (branch 2661). Pls go ahead merge.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1391d5c444782ac300b2e570302f601e19ceb3f9

commit 1391d5c444782ac300b2e570302f601e19ceb3f9
Author: Xianzhu Wang <wangxianzhu@chromium.org>
Date: Mon Apr 11 23:16:11 2016

Update PaintLayer::needsPaintPhaseXXX flags when add/remove layer on style change

When addding/removing a layer on style change, we may not
do paint invalidation to update the needsPaintPhaseXXX flags, so
we need to update the flags manually.

In the future, the logic can be simplified by updating the flags
during pre-painting tree walk.

BUG= 598978 

Review URL: https://codereview.chromium.org/1862313002

Cr-Commit-Position: refs/heads/master@{#386264}

Review URL: https://codereview.chromium.org/1877093002 .

Cr-Commit-Position: refs/branch-heads/2661@{#558}
Cr-Branched-From: ef6f6ae5e4c96622286b563658d5cd62a6cf1197-refs/heads/master@{#378081}

[modify] https://crrev.com/1391d5c444782ac300b2e570302f601e19ceb3f9/third_party/WebKit/Source/core/layout/LayoutBoxModelObject.cpp
[modify] https://crrev.com/1391d5c444782ac300b2e570302f601e19ceb3f9/third_party/WebKit/Source/core/layout/LayoutObject.cpp
[modify] https://crrev.com/1391d5c444782ac300b2e570302f601e19ceb3f9/third_party/WebKit/Source/core/paint/PaintLayer.cpp
[modify] https://crrev.com/1391d5c444782ac300b2e570302f601e19ceb3f9/third_party/WebKit/Source/core/paint/PaintLayer.h
[modify] https://crrev.com/1391d5c444782ac300b2e570302f601e19ceb3f9/third_party/WebKit/Source/core/paint/PaintLayerPainterTest.cpp
[modify] https://crrev.com/1391d5c444782ac300b2e570302f601e19ceb3f9/third_party/WebKit/Source/core/paint/README.md

Verified the fix on MAC (10.11.4) for Google Chrome Beta Version - 50.0.2661.75 

Screen-recording is attached.

TE-Verified labels are added.

Deleted: 598978.mov 5.8 MB

598978.mov 5.8 MB Download

The CL missed m51 branch point. Request merge to m51.

Your change meets the bar and is auto-approved for M51 (branch: 2704)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e921b6e5f7720bee35402813ac14707eb6028480

commit e921b6e5f7720bee35402813ac14707eb6028480
Author: Xianzhu Wang <wangxianzhu@chromium.org>
Date: Thu Apr 14 16:13:21 2016

Update PaintLayer::needsPaintPhaseXXX flags when add/remove layer on style change

When addding/removing a layer on style change, we may not
do paint invalidation to update the needsPaintPhaseXXX flags, so
we need to update the flags manually.

In the future, the logic can be simplified by updating the flags
during pre-painting tree walk.

BUG= 598978 

Review URL: https://codereview.chromium.org/1862313002

Cr-Commit-Position: refs/heads/master@{#386264}

Review URL: https://codereview.chromium.org/1892473002 .

Cr-Commit-Position: refs/branch-heads/2704@{#54}
Cr-Branched-From: 6e53600def8f60d8c632fadc70d7c1939ccea347-refs/heads/master@{#386251}

[modify] https://crrev.com/e921b6e5f7720bee35402813ac14707eb6028480/third_party/WebKit/Source/core/layout/LayoutBoxModelObject.cpp
[modify] https://crrev.com/e921b6e5f7720bee35402813ac14707eb6028480/third_party/WebKit/Source/core/layout/LayoutObject.cpp
[modify] https://crrev.com/e921b6e5f7720bee35402813ac14707eb6028480/third_party/WebKit/Source/core/paint/PaintLayer.cpp
[modify] https://crrev.com/e921b6e5f7720bee35402813ac14707eb6028480/third_party/WebKit/Source/core/paint/PaintLayer.h
[modify] https://crrev.com/e921b6e5f7720bee35402813ac14707eb6028480/third_party/WebKit/Source/core/paint/PaintLayerPainterTest.cpp
[modify] https://crrev.com/e921b6e5f7720bee35402813ac14707eb6028480/third_party/WebKit/Source/core/paint/README.md

Verified the issue on Mac OS 10.11.4 using chrome latest Dev M51-51.0.2704.19 and observed the page https://www.travelchinaguide.com/essential/public-holiday.htm is opening completely as expected in the low dpi monitor. Hence adding TE-Verified label.

Deleted: Screen Shot 2016-04-19 at 11.57.03 AM.png 366 KB

	Screen Shot 2016-04-19 at 11.57.03 AM.png 366 KB View Download