To repro:
1) Start debug content shell with --enable-slimming-paint-v2
2) Visit https://www.google.com/?gws_rd=ssl#q=d

[82152:1295:0817/222715:2313093832177207:FATAL:PaintController.cpp(382)] Check failed: (!m_newPaintChunks.lastChunk().id && !cachedChunk->id) || m_newPaintChunks.lastChunk().matches(*cachedChunk). 
0   libbase.dylib           _ZN4base5debug10StackTraceC2Ev + 30
1   libbase.dylib           _ZN4base5debug10StackTraceC1Ev + 21
2   libbase.dylib           _ZN7logging10LogMessageD2Ev + 80
3   libbase.dylib           _ZN7logging10LogMessageD1Ev + 21
4   libblink_platform.dylib _ZN5blink15PaintController21copyCachedSubsequenceERm + 1883
5   libblink_platform.dylib _ZN5blink15PaintController30useCachedSubsequenceIfPossibleERKNS_17DisplayItemClientE + 396
6   libblink_core.dylib     _ZN5blink19SubsequenceRecorder30useCachedSubsequenceIfPossibleERNS_15GraphicsContextERKNS_17DisplayItemClientE + 37
7   libblink_core.dylib     _ZN5blink17PaintLayerPainter18paintLayerContentsERNS_15GraphicsContextERKNS_22PaintLayerPaintingInfoEjNS0_14FragmentPolicyE + 1159
8   libblink_core.dylib     _ZN5blink17PaintLayerPainter31paintLayerContentsAndReflectionERNS_15GraphicsContextERKNS_22PaintLayerPaintingInfoEjNS0_14FragmentPolicyE + 306
9   libblink_core.dylib     _ZN5blink17PaintLayerPainter10paintLayerERNS_15GraphicsContextERKNS_22PaintLayerPaintingInfoEj + 596
10  libblink_core.dylib     _ZN5blink17PaintLayerPainter13paintChildrenEjRNS_15GraphicsContextERKNS_22PaintLayerPaintingInfoEj + 650
11  libblink_core.dylib     _ZN5blink17PaintLayerPainter18paintLayerContentsERNS_15GraphicsContextERKNS_22PaintLayerPaintingInfoEjNS0_14FragmentPolicyE + 4397
12  libblink_core.dylib     _ZN5blink17PaintLayerPainter31paintLayerContentsAndReflectionERNS_15GraphicsContextERKNS_22PaintLayerPaintingInfoEjNS0_14FragmentPolicyE + 306
13  libblink_core.dylib     _ZN5blink17PaintLayerPainter10paintLayerERNS_15GraphicsContextERKNS_22PaintLayerPaintingInfoEj + 596
14  libblink_core.dylib     _ZN5blink17PaintLayerPainter13paintChildrenEjRNS_15GraphicsContextERKNS_22PaintLayerPaintingInfoEj + 650
15  libblink_core.dylib     _ZN5blink17PaintLayerPainter18paintLayerContentsERNS_15GraphicsContextERKNS_22PaintLayerPaintingInfoEjNS0_14FragmentPolicyE + 4397
16  libblink_core.dylib     _ZNK5blink22CompositedLayerMapping11doPaintTaskERKNS_22GraphicsLayerPaintInfoERKNS_13GraphicsLayerERKjRNS_15GraphicsContextERKNS_7IntRectE + 782
17  libblink_core.dylib     _ZNK5blink22CompositedLayerMapping13paintContentsEPKNS_13GraphicsLayerERNS_15GraphicsContextEjRKNS_7IntRectE + 2273
18  libblink_platform.dylib _ZN5blink13GraphicsLayer18paintWithoutCommitEPKNS_7IntRectENS_15GraphicsContext12DisabledModeE + 635
19  libblink_platform.dylib _ZN5blink13GraphicsLayer5paintEPKNS_7IntRectENS_15GraphicsContext12DisabledModeE + 80
20  libblink_core.dylib     _ZN5blink9FrameView28synchronizedPaintRecursivelyEPNS_13GraphicsLayerE + 61