Change StyleResolverState.styleImage() to take a const CSSValue&

Change StyleResolverState.styleImage() to take a const CSSValue&

Change StyleResolverState.styleImage to take a const CSSValue& instead
of a CSSValue*. This involved changing most ElementStyleResources
functions to do the same. Also introduced some const_casts into
StylePendingImage and StyleGeneratedImage since RefPtr<> currently
doesn't support storing const objects.

This is required to enable CSSToStyleMap to take const CSSValue&s.

BUG=526586
Committed: https://crrev.com/4ee57fcf43daf1b7dea8dd6bf9f1858b1b60f24b
Cr-Commit-Position: refs/heads/master@{#352761}

[sashab, 2015-10-06 03:41:04]

sashab@chromium.org changed reviewers:
+ timloh@chromium.org

[sashab, 2015-10-06 03:41:05]

Tim; wdyt? I could add accessors to the non-const RefPtrWillBeMember<>s that
make them const, and make the class work correctly with these as 'const'
members. i.e.:

private:
  RefPtrWillBeMember<CSSValue> m_value;
  const CSSValue& value() const { return const_cast<const CSSValue&>(*m_value);
}

Right now they don't need any more mutable/const fields since m_value is not
const.

[Timothy Loh, 2015-10-07 00:47:54]

lgtm

[sashab, 2015-10-07 00:49:49]

The CQ bit was checked by sashab@chromium.org

[commit-bot: I haz the power, 2015-10-07 00:52:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1387113002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1387113002/20001

[alancutter (OOO until 2018), 2015-10-07 03:28:27]

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

[alancutter (OOO until 2018), 2015-10-07 03:28:28]

https://codereview.chromium.org/1387113002/diff/20001/third_party/WebKit/Sour...
File third_party/WebKit/Source/core/style/StylePendingImage.h (right):

https://codereview.chromium.org/1387113002/diff/20001/third_party/WebKit/Sour...
third_party/WebKit/Source/core/style/StylePendingImage.h:44: static
PassRefPtrWillBeRawPtr<StylePendingImage> create(const CSSValue& value)
I don't think we should break the pattern of create() methods taking
PassRefPtrs. I would prefer to see the const_cast at the call sites to create().
I expect one day we will have create(PassRefPtr<const CSSValue>).

[commit-bot: I haz the power, 2015-10-07 03:45:33]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-10-07 03:47:06]

Patchset 2 (id:??) landed as
https://crrev.com/4ee57fcf43daf1b7dea8dd6bf9f1858b1b60f24b
Cr-Commit-Position: refs/heads/master@{#352761}