The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b5aa6bf1f11d6e94548b10f12a245933c78a0cfb

commit b5aa6bf1f11d6e94548b10f12a245933c78a0cfb
Author: Becca Hughes <beccahughes@chromium.org>
Date: Thu May 31 22:13:01 2018

[CSS Env Vars] Parse env()

Parse environment variables using the env() syntax. This does
not include resolving them which will be in a subsequent CL.

BUG= 847651 

Change-Id: I80f502afe53146da6cc58b450b20c6b1c323d354
Reviewed-on: https://chromium-review.googlesource.com/1077589
Commit-Queue: Becca Hughes <beccahughes@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#563396}
[modify] https://crrev.com/b5aa6bf1f11d6e94548b10f12a245933c78a0cfb/third_party/blink/renderer/core/BUILD.gn
[modify] https://crrev.com/b5aa6bf1f11d6e94548b10f12a245933c78a0cfb/third_party/blink/renderer/core/css/CSSValueKeywords.json5
[modify] https://crrev.com/b5aa6bf1f11d6e94548b10f12a245933c78a0cfb/third_party/blink/renderer/core/css/cssom/css_unparsed_value.cc
[modify] https://crrev.com/b5aa6bf1f11d6e94548b10f12a245933c78a0cfb/third_party/blink/renderer/core/css/parser/css_variable_parser.cc
[modify] https://crrev.com/b5aa6bf1f11d6e94548b10f12a245933c78a0cfb/third_party/blink/renderer/core/css/resolver/css_variable_resolver.cc
[modify] https://crrev.com/b5aa6bf1f11d6e94548b10f12a245933c78a0cfb/third_party/blink/renderer/core/css/resolver/css_variable_resolver.h
[add] https://crrev.com/b5aa6bf1f11d6e94548b10f12a245933c78a0cfb/third_party/blink/renderer/core/css/resolver/css_variable_resolver_test.cc
[modify] https://crrev.com/b5aa6bf1f11d6e94548b10f12a245933c78a0cfb/third_party/blink/renderer/platform/runtime_enabled_features.json5

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e04b630822af76d605349a5da8786cf2aec9a180

commit e04b630822af76d605349a5da8786cf2aec9a180
Author: Becca Hughes <beccahughes@chromium.org>
Date: Fri Jun 01 19:47:25 2018

[CSS Env Vars] Resolve & invalidate variables

Adds a StyleEnvironmentVariables class to store names and
values of env() variables. There is a static per-renderer
instance that is the root and stores global variables.

There is also a document specific version of this class
that is bound to a Document and is a child of the static
class. This stores document level variables.

Updating a variable will trigger an invalidation on the
documents that are using the variable.

BUG= 847651 

Change-Id: Ia86b52a955c32c5e9d8c0a6953e50cc0958131a7
Reviewed-on: https://chromium-review.googlesource.com/1081491
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Commit-Queue: Becca Hughes <beccahughes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#563762}
[modify] https://crrev.com/e04b630822af76d605349a5da8786cf2aec9a180/third_party/blink/renderer/core/BUILD.gn
[modify] https://crrev.com/e04b630822af76d605349a5da8786cf2aec9a180/third_party/blink/renderer/core/css/BUILD.gn
[add] https://crrev.com/e04b630822af76d605349a5da8786cf2aec9a180/third_party/blink/renderer/core/css/document_style_environment_variables.cc
[add] https://crrev.com/e04b630822af76d605349a5da8786cf2aec9a180/third_party/blink/renderer/core/css/document_style_environment_variables.h
[modify] https://crrev.com/e04b630822af76d605349a5da8786cf2aec9a180/third_party/blink/renderer/core/css/resolver/css_variable_resolver.cc
[modify] https://crrev.com/e04b630822af76d605349a5da8786cf2aec9a180/third_party/blink/renderer/core/css/resolver/css_variable_resolver_test.cc
[modify] https://crrev.com/e04b630822af76d605349a5da8786cf2aec9a180/third_party/blink/renderer/core/css/style_engine.cc
[modify] https://crrev.com/e04b630822af76d605349a5da8786cf2aec9a180/third_party/blink/renderer/core/css/style_engine.h
[add] https://crrev.com/e04b630822af76d605349a5da8786cf2aec9a180/third_party/blink/renderer/core/css/style_environment_variables.cc
[add] https://crrev.com/e04b630822af76d605349a5da8786cf2aec9a180/third_party/blink/renderer/core/css/style_environment_variables.h
[add] https://crrev.com/e04b630822af76d605349a5da8786cf2aec9a180/third_party/blink/renderer/core/css/style_environment_variables_test.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/90e2795754aaf6e82ab27b9403d9367cea4b1936

commit 90e2795754aaf6e82ab27b9403d9367cea4b1936
Author: Mostyn Bramley-Moore <mostynb@vewd.com>
Date: Fri Jun 01 22:25:15 2018

[jumbo] avoid redefinition of kTestColor const

https://chromium-review.googlesource.com/c/chromium/src/+/1081491 introduced
two anonymous-namespaced kTestColor's in two source files that end up in
the same jumbo unit.  Let's rename one.

BUG= 847651 

Change-Id: I92840266f9a96619985810c646927dee24353b3f
Reviewed-on: https://chromium-review.googlesource.com/1083193
Reviewed-by: Becca Hughes <beccahughes@chromium.org>
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Commit-Queue: Mostyn Bramley-Moore <mostynb@vewd.com>
Commit-Queue: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#563834}
[modify] https://crrev.com/90e2795754aaf6e82ab27b9403d9367cea4b1936/third_party/blink/renderer/core/css/style_environment_variables_test.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b2491b1fef4a059d63b1541d448317cb0604b9a6

commit b2491b1fef4a059d63b1541d448317cb0604b9a6
Author: Becca Hughes <beccahughes@chromium.org>
Date: Sat Jun 02 00:07:44 2018

[CSS Env Vars] Move feature to experimental

Move CSS env() to experimental so it can be toggled
from about://flags.

BUG= 847651 

Change-Id: Ic1de147f097bcebe64a6783c6be7217f046f4532
Reviewed-on: https://chromium-review.googlesource.com/1083812
Commit-Queue: Becca Hughes <beccahughes@chromium.org>
Commit-Queue: Emil A Eklund <eae@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#563873}
[modify] https://crrev.com/b2491b1fef4a059d63b1541d448317cb0604b9a6/third_party/blink/renderer/platform/runtime_enabled_features.json5

There are still some bits to do around user defined properties and feature detection but these are separate bugs. The core implementation is done so I will close this for now.

@Becca please note 855134