Make TreeScope::documentScope() return a reference and ensure m_documentScope is never NULL

Make TreeScope::documentScope() return a reference and ensure m_documentScope is never NULL

The only big change is the removal of TreeScope::clearDocumentScope().
Now that documentScope() always returns a reference, no caller should even be
able to deal with it being null. And since we already ASSERT in ~Document and ~TreeScope
that guardRefCount is 0, there should be no one else with a reference to this TreeScope.
Thus, the call to setTreeScope(0) in ~TreeScope should be sufficient to avoid a
use-after-free of |this| as a Document. 

The rest of the lines touched in this patch are just pointer -> reference conversion.

Also removed the unused default TreeScope constructor.

BUG=331922
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=164586

[esprehn, 2014-01-07 01:06:09]

lgtm

https://codereview.chromium.org/112953007/diff/1/Source/core/css/StyleSheetLi...
File Source/core/css/StyleSheetList.h (right):

https://codereview.chromium.org/112953007/diff/1/Source/core/css/StyleSheetLi...
Source/core/css/StyleSheetList.h:46: Document* document() { return
&m_treeScope->documentScope(); }
FIXME: should return a reference?

https://codereview.chromium.org/112953007/diff/1/Source/core/dom/StyleSheetCo...
File Source/core/dom/StyleSheetCollection.h (right):

https://codereview.chromium.org/112953007/diff/1/Source/core/dom/StyleSheetCo...
Source/core/dom/StyleSheetCollection.h:96: Document* document() { return
&m_treeScope.documentScope(); }
FIXME: should return a reference.

[adamk, 2014-01-07 01:11:12]

https://codereview.chromium.org/112953007/diff/1/Source/core/css/StyleSheetLi...
File Source/core/css/StyleSheetList.h (right):

https://codereview.chromium.org/112953007/diff/1/Source/core/css/StyleSheetLi...
Source/core/css/StyleSheetList.h:46: Document* document() { return
&m_treeScope->documentScope(); }
On 2014/01/07 01:06:09, esprehn wrote:
> FIXME: should return a reference?

Done.

https://codereview.chromium.org/112953007/diff/1/Source/core/dom/StyleSheetCo...
File Source/core/dom/StyleSheetCollection.h (right):

https://codereview.chromium.org/112953007/diff/1/Source/core/dom/StyleSheetCo...
Source/core/dom/StyleSheetCollection.h:96: Document* document() { return
&m_treeScope.documentScope(); }
On 2014/01/07 01:06:09, esprehn wrote:
> FIXME: should return a reference.

Done.

[commit-bot: I haz the power, 2014-01-07 01:11:30]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/adamk@chromium.org/112953007/110001

[commit-bot: I haz the power, 2014-01-07 13:44:24]

Retried try job too often on win_blink_rel for step(s) webkit_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_blink_...

[commit-bot: I haz the power, 2014-01-07 13:53:00]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/adamk@chromium.org/112953007/110001

[commit-bot: I haz the power, 2014-01-07 14:59:30]

Change committed as 164586