The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6d10aad7a6f28294851e37f6ab7f0b0ac5086508

commit 6d10aad7a6f28294851e37f6ab7f0b0ac5086508
Author: Darren Shen <shend@chromium.org>
Date: Fri Feb 02 04:40:36 2018

[css-typed-om] Refactor CSSStyleImageValue to prepare for gradients.

Currently CSSStyleImageValue implements the CSSImageValue class in
Typed OM. CSSImageValue can be anything that's an <image> i.e. a <url>,
<gradient>, or <cross-fade>.

However, the current implementation of CSSStyleImageValue only really
works for <url>s. This patch moves <url> specific logic into
CSSURLImageValue. This prepares for the implementation of <gradient> and
<cross-fade>, which will be subclasses of CSSStyleImageValue.

We also do some cleanup work (e.g. making things const, moving code in
header to cpp).

Bug: 803680
Change-Id: I848b3eab5dbbcb9bbe7f0aea0d377497f63bfda3
Reviewed-on: https://chromium-review.googlesource.com/882786
Commit-Queue: Darren Shen <shend@chromium.org>
Reviewed-by: nainar <nainar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533949}
[modify] https://crrev.com/6d10aad7a6f28294851e37f6ab7f0b0ac5086508/third_party/WebKit/Source/core/css/BUILD.gn
[modify] https://crrev.com/6d10aad7a6f28294851e37f6ab7f0b0ac5086508/third_party/WebKit/Source/core/css/cssom/CSSStyleImageValue.cpp
[modify] https://crrev.com/6d10aad7a6f28294851e37f6ab7f0b0ac5086508/third_party/WebKit/Source/core/css/cssom/CSSStyleImageValue.h
[modify] https://crrev.com/6d10aad7a6f28294851e37f6ab7f0b0ac5086508/third_party/WebKit/Source/core/css/cssom/CSSStyleImageValueTest.cpp
[add] https://crrev.com/6d10aad7a6f28294851e37f6ab7f0b0ac5086508/third_party/WebKit/Source/core/css/cssom/CSSURLImageValue.cpp
[modify] https://crrev.com/6d10aad7a6f28294851e37f6ab7f0b0ac5086508/third_party/WebKit/Source/core/css/cssom/CSSURLImageValue.h
[modify] https://crrev.com/6d10aad7a6f28294851e37f6ab7f0b0ac5086508/third_party/WebKit/Source/core/css/cssom/StyleValueFactory.cpp

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1f977216838ab364205dcd288b0b3efc0de1b01d

commit 1f977216838ab364205dcd288b0b3efc0de1b01d
Author: Yuta Kitamura <yutak@chromium.org>
Date: Fri Feb 02 08:56:54 2018

Revert "[css-typed-om] Refactor CSSStyleImageValue to prepare for gradients."

This reverts commit 6d10aad7a6f28294851e37f6ab7f0b0ac5086508.

Reason for revert: Caused MSAN bot failure.

https://ci.chromium.org/buildbot/chromium.memory/Linux%20MSan%20Tests/7639

Original change's description:
> [css-typed-om] Refactor CSSStyleImageValue to prepare for gradients.
> 
> Currently CSSStyleImageValue implements the CSSImageValue class in
> Typed OM. CSSImageValue can be anything that's an <image> i.e. a <url>,
> <gradient>, or <cross-fade>.
> 
> However, the current implementation of CSSStyleImageValue only really
> works for <url>s. This patch moves <url> specific logic into
> CSSURLImageValue. This prepares for the implementation of <gradient> and
> <cross-fade>, which will be subclasses of CSSStyleImageValue.
> 
> We also do some cleanup work (e.g. making things const, moving code in
> header to cpp).
> 
> Bug: 803680
> Change-Id: I848b3eab5dbbcb9bbe7f0aea0d377497f63bfda3
> Reviewed-on: https://chromium-review.googlesource.com/882786
> Commit-Queue: Darren Shen <shend@chromium.org>
> Reviewed-by: nainar <nainar@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#533949}

TBR=nainar@chromium.org,shend@chromium.org

Change-Id: I9aedca3ac9e3ecb07ed283447febede0628d7aeb
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 803680
Reviewed-on: https://chromium-review.googlesource.com/896671
Reviewed-by: Yuta Kitamura <yutak@chromium.org>
Commit-Queue: Yuta Kitamura <yutak@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534002}
[modify] https://crrev.com/1f977216838ab364205dcd288b0b3efc0de1b01d/third_party/WebKit/Source/core/css/BUILD.gn
[modify] https://crrev.com/1f977216838ab364205dcd288b0b3efc0de1b01d/third_party/WebKit/Source/core/css/cssom/CSSStyleImageValue.cpp
[modify] https://crrev.com/1f977216838ab364205dcd288b0b3efc0de1b01d/third_party/WebKit/Source/core/css/cssom/CSSStyleImageValue.h
[modify] https://crrev.com/1f977216838ab364205dcd288b0b3efc0de1b01d/third_party/WebKit/Source/core/css/cssom/CSSStyleImageValueTest.cpp
[delete] https://crrev.com/6134471c6a971ab2e9707889c5bc0332397fc551/third_party/WebKit/Source/core/css/cssom/CSSURLImageValue.cpp
[modify] https://crrev.com/1f977216838ab364205dcd288b0b3efc0de1b01d/third_party/WebKit/Source/core/css/cssom/CSSURLImageValue.h
[modify] https://crrev.com/1f977216838ab364205dcd288b0b3efc0de1b01d/third_party/WebKit/Source/core/css/cssom/StyleValueFactory.cpp

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d9a71c341af98d201c3c2cafc12f47612444db76

commit d9a71c341af98d201c3c2cafc12f47612444db76
Author: Darren Shen <shend@chromium.org>
Date: Mon Feb 05 04:52:59 2018

Revert "Revert "[css-typed-om] Refactor CSSStyleImageValue to prepare for gradients.""

This reverts commit 1f977216838ab364205dcd288b0b3efc0de1b01d.

Reason for revert: Relanding

Original change's description:
> Revert "[css-typed-om] Refactor CSSStyleImageValue to prepare for gradients."
> 
> This reverts commit 6d10aad7a6f28294851e37f6ab7f0b0ac5086508.
> 
> Reason for revert: Caused MSAN bot failure.
> 
> https://ci.chromium.org/buildbot/chromium.memory/Linux%20MSan%20Tests/7639
> 
> Original change's description:
> > [css-typed-om] Refactor CSSStyleImageValue to prepare for gradients.
> > 
> > Currently CSSStyleImageValue implements the CSSImageValue class in
> > Typed OM. CSSImageValue can be anything that's an <image> i.e. a <url>,
> > <gradient>, or <cross-fade>.
> > 
> > However, the current implementation of CSSStyleImageValue only really
> > works for <url>s. This patch moves <url> specific logic into
> > CSSURLImageValue. This prepares for the implementation of <gradient> and
> > <cross-fade>, which will be subclasses of CSSStyleImageValue.
> > 
> > We also do some cleanup work (e.g. making things const, moving code in
> > header to cpp).
> > 
> > Bug: 803680
> > Change-Id: I848b3eab5dbbcb9bbe7f0aea0d377497f63bfda3
> > Reviewed-on: https://chromium-review.googlesource.com/882786
> > Commit-Queue: Darren Shen <shend@chromium.org>
> > Reviewed-by: nainar <nainar@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#533949}
> 
> TBR=nainar@chromium.org,shend@chromium.org
> 
> Change-Id: I9aedca3ac9e3ecb07ed283447febede0628d7aeb
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 803680
> Reviewed-on: https://chromium-review.googlesource.com/896671
> Reviewed-by: Yuta Kitamura <yutak@chromium.org>
> Commit-Queue: Yuta Kitamura <yutak@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#534002}

TBR=yutak@chromium.org,nainar@chromium.org,shend@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 803680
Change-Id: Iccabf87cde1e9bd30ab1d08e31fe1b774a59f029
Reviewed-on: https://chromium-review.googlesource.com/900563
Commit-Queue: Darren Shen <shend@chromium.org>
Reviewed-by: Darren Shen <shend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534328}
[modify] https://crrev.com/d9a71c341af98d201c3c2cafc12f47612444db76/third_party/WebKit/Source/core/css/BUILD.gn
[modify] https://crrev.com/d9a71c341af98d201c3c2cafc12f47612444db76/third_party/WebKit/Source/core/css/cssom/CSSStyleImageValue.cpp
[modify] https://crrev.com/d9a71c341af98d201c3c2cafc12f47612444db76/third_party/WebKit/Source/core/css/cssom/CSSStyleImageValue.h
[modify] https://crrev.com/d9a71c341af98d201c3c2cafc12f47612444db76/third_party/WebKit/Source/core/css/cssom/CSSStyleImageValueTest.cpp
[add] https://crrev.com/d9a71c341af98d201c3c2cafc12f47612444db76/third_party/WebKit/Source/core/css/cssom/CSSURLImageValue.cpp
[modify] https://crrev.com/d9a71c341af98d201c3c2cafc12f47612444db76/third_party/WebKit/Source/core/css/cssom/CSSURLImageValue.h
[modify] https://crrev.com/d9a71c341af98d201c3c2cafc12f47612444db76/third_party/WebKit/Source/core/css/cssom/StyleValueFactory.cpp

There's a patch ready in [1], but we're close to branch point and I'm slightly worried that there are some subtle bugs to do with caching of resources. This shouldn't too big a deal, as the canvas can already draw gradients by itself.

[1] https://chromium-review.googlesource.com/c/chromium/src/+/882906

If this is not critical, I'll land it after branch point for safety.

No longer working on Typed OM, marking as Available. The patch in #c5 should work, but I was worried it degrades performance because of an additional virtual call. Would be great if there's a better way to do this.