Add mutableComponent() interface to InterpolationValue

Add mutableComponent() interface to InterpolationValue

This change is a simple refactor to make mutation of InterpolationValues
clear in preparation of adding a composite() method to InterpolationType
which will operate on UnderlyingValues.

This also isolates the InterpolableValue + NonInterpolableValue pair
as an InterpolationComponentValue for easier data transfer to be used
by future static InterpolationType conversion methods.

This introduces no change in behaviour.

BUG=437696
Committed: https://crrev.com/1819b0342299d7b8054bc11aefb72e6d3768bb6d
git-svn-id: svn://svn.chromium.org/blink/trunk@202176 bbb929c8-8fbe-4397-9dbb-9b2b20218538

[alancutter (OOO until 2018), 2015-09-09 05:32:30]

alancutter@chromium.org changed reviewers:
+ dstockwell@chromium.org, shans@chromium.org

[dstockwell, 2015-09-14 00:24:36]

lgtm

https://codereview.chromium.org/1318143005/diff/1/Source/core/animation/Inter...
File Source/core/animation/InterpolationValue.h (right):

https://codereview.chromium.org/1318143005/diff/1/Source/core/animation/Inter...
Source/core/animation/InterpolationValue.h:44: InterpolationComponentValue&
mutableComponent() { return m_component; }
The component naming doesn't help here, this sounds like "give me the mutable
part of the larger structure".

[alancutter (OOO until 2018), 2015-09-14 00:37:39]

https://codereview.chromium.org/1318143005/diff/1/Source/core/animation/Inter...
File Source/core/animation/InterpolationValue.h (right):

https://codereview.chromium.org/1318143005/diff/1/Source/core/animation/Inter...
Source/core/animation/InterpolationValue.h:44: InterpolationComponentValue&
mutableComponent() { return m_component; }
On 2015/09/14 at 00:24:36, dstockwell wrote:
> The component naming doesn't help here, this sounds like "give me the mutable
part of the larger structure".

This description is an accurate interpretation of the data structure and
purpose.

[alancutter (OOO until 2018), 2015-09-14 00:38:48]

The CQ bit was checked by alancutter@chromium.org

[commit-bot: I haz the power, 2015-09-14 00:39:00]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1318143005/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1318143005/1

[commit-bot: I haz the power, 2015-09-14 05:09:48]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=202176

[commit-bot: I haz the power, 2015-09-23 12:29:32]

Patchset 1 (id:??) landed as
https://crrev.com/1819b0342299d7b8054bc11aefb72e6d3768bb6d