Use CSSPrimitiveValue::create in CSSLengthInterpolationType

Use CSSPrimitiveValue::create in CSSLengthInterpolationType

This change removes unnecessary code to convert an interpolable length
into a CSS value by reusing existing code that converts a Length object
into a CSSPrimitiveValue.
This change also fixes up the assertion in CSSLengthInterpolationType::apply
to not depend on AnimatableValues as well as making the surrounding comment
more accurate as to its intentions.

BUG=630487
Committed: https://crrev.com/830c24aa142db9bb04ca3ca74fce50636dd724b7
Cr-Commit-Position: refs/heads/master@{#416851}

[alancutter (OOO until 2018), 2016-09-05 07:29:10]

alancutter@chromium.org changed reviewers:
+ suzyh@chromium.org

[alancutter (OOO until 2018), 2016-09-05 07:29:11]

https://codereview.chromium.org/2314453002/diff/1/third_party/WebKit/Source/c...
File third_party/WebKit/Source/core/animation/CSSLengthInterpolationType.cpp
(right):

https://codereview.chromium.org/2314453002/diff/1/third_party/WebKit/Source/c...
third_party/WebKit/Source/core/animation/CSSLengthInterpolationType.cpp:275:
DCHECK(before == after);
This does not use DCHECK_EQ because Length is not serialisable.

[suzyh_UTC10 (ex-contributor), 2016-09-06 00:15:41]

lgtm

[alancutter (OOO until 2018), 2016-09-06 00:27:25]

The CQ bit was checked by alancutter@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-09-06 00:27:27]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-09-06 01:59:04]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-09-06 01:59:04]

Dry run: This issue passed the CQ dry run.

[alancutter (OOO until 2018), 2016-09-07 03:56:30]

The CQ bit was checked by alancutter@chromium.org

[commit-bot: I haz the power, 2016-09-07 03:56:49]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-09-07 05:28:06]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-09-07 05:30:33]

Description was changed from

==========
Use CSSPrimitiveValue::create in CSSLengthInterpolationType

This change removes unnecessary code to convert an interpolable length
into a CSS value by reusing existing code that converts a Length object
into a CSSPrimitiveValue.
This change also fixes up the assertion in CSSLengthInterpolationType::apply
to not depend on AnimatableValues as well as making the surrounding comment
more accurate as to its intentions.

BUG=630487
==========

to

==========
Use CSSPrimitiveValue::create in CSSLengthInterpolationType

This change removes unnecessary code to convert an interpolable length
into a CSS value by reusing existing code that converts a Length object
into a CSSPrimitiveValue.
This change also fixes up the assertion in CSSLengthInterpolationType::apply
to not depend on AnimatableValues as well as making the surrounding comment
more accurate as to its intentions.

BUG=630487

Committed: https://crrev.com/830c24aa142db9bb04ca3ca74fce50636dd724b7
Cr-Commit-Position: refs/heads/master@{#416851}
==========

[commit-bot: I haz the power, 2016-09-07 05:30:34]

Patchset 1 (id:??) landed as
https://crrev.com/830c24aa142db9bb04ca3ca74fce50636dd724b7
Cr-Commit-Position: refs/heads/master@{#416851}