I am unable to completely rebaseline the Blink layout tests for my CL (https://chromium-review.googlesource.com/c/chromium/src/+/1335871/13). Here's what I get after all trybots have finished running:

$ third_party/blink/tools/blink_tool.py rebaseline-cl

2018-12-20 16:07:14,806 - Finished try jobs found for all try bots.
2018-12-20 16:07:37,999 - No retry summary available for "mac10.13-blink-rel".
2018-12-20 16:07:38,394 - No retry summary available for "mac10.11-blink-rel".
2018-12-20 16:07:38,695 - No retry summary available for "mac10.13_retina-blink-rel".
2018-12-20 16:07:39,095 - No retry summary available for "mac10.12-blink-rel".
2018-12-20 16:07:40,293 - No retry summary available for "mac10.10-blink-rel".
2018-12-20 16:07:41,014 - Rebaselining compositing/background-color/background-color-alpha.html
2018-12-20 16:07:41,014 - Rebaselining compositing/overflow/clip-content-under-overflow-controls.html
2018-12-20 16:07:41,014 - Rebaselining compositing/scrollbar-painting.html
2018-12-20 16:07:41,014 - Rebaselining transforms/3d/point-mapping/3d-point-mapping-overlapping.html
2018-12-20 16:07:41,014 - Rebaselining virtual/prefer_compositing_to_lcd_text/compositing/overflow/clip-content-under-overflow-controls.html
2018-12-20 16:07:41,014 - Rebaselining virtual/stable/compositing/background-color/background-color-alpha.html
2018-12-20 16:07:41,014 - Rebaselining virtual/stable/compositing/overflow/clip-content-under-overflow-controls.html
2018-12-20 16:07:41,014 - Rebaselining virtual/stable/compositing/scrollbar-painting.html
2018-12-20 16:08:20,725 - 2018-12-20 16:08:03,928 - Cannot rebaseline image result for reftest: compositing/background-color/background-color-alpha.html

2018-12-20 16:08:20,725 - 2018-12-20 16:08:03,927 - Cannot rebaseline image result for reftest: compositing/background-color/background-color-alpha.html

2018-12-20 16:08:20,725 - 2018-12-20 16:08:03,947 - Cannot rebaseline image result for reftest: compositing/background-color/background-color-alpha.html

2018-12-20 16:08:20,725 - 2018-12-20 16:08:03,926 - Cannot rebaseline image result for reftest: compositing/background-color/background-color-alpha.html

2018-12-20 16:08:20,725 - 2018-12-20 16:08:03,933 - Cannot rebaseline image result for reftest: compositing/background-color/background-color-alpha.html

2018-12-20 16:08:20,725 - 2018-12-20 16:08:04,048 - Cannot rebaseline image result for reftest: compositing/background-color/background-color-alpha.html

2018-12-20 16:08:20,725 - 2018-12-20 16:08:04,054 - Cannot rebaseline image result for reftest: compositing/background-color/background-color-alpha.html

2018-12-20 16:08:20,725 - 2018-12-20 16:08:04,053 - Cannot rebaseline image result for reftest: compositing/background-color/background-color-alpha.html

2018-12-20 16:08:20,725 - 2018-12-20 16:08:06,536 - Cannot rebaseline image result for reftest: virtual/stable/compositing/background-color/background-color-alpha.html