IDL compiler: [CustomToV8] interface

BUG=239771

Review URL: https://codereview.chromium.org/82693003

git-svn-id: svn://svn.chromium.org/blink/trunk@163153 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Extract HTMLImportData from HTMLImportLoader

This change is a preparation of crbug.com/306292.
To fix it, an import tree loader needs "pending" state
and wait preceeding import being loaded.

This change extract HTMLImportData from HTMLImportLoader,
which allows the loader to be "pending" state, by
having null "data" object.

To dedup imports, each HTMLImportData object can be shared
by multiple loaders. Before this change, the loader was
shared for handling duplication.

BUG=306292
R=dglazkov, tkent
TEST=none

Review URL: https://codereview.chromium.org/93953002

git-svn-id: svn://svn.chromium.org/blink/trunk@163154 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[HTML Imports] Support linked stylesheet

This change unblocks stylesheet links in imported documents being loaded.
As stylesheet loading should block script execution, the style links
in imports tells the master document that it is loading a stylesheet.

BUG=319151
R=esprehn,ojan,dglazkov
TEST=import-style-link.html

Review URL: https://codereview.chromium.org/94103004

git-svn-id: svn://svn.chromium.org/blink/trunk@163155 bbb929c8-8fbe-4397-9dbb-9b2b20218538