Remove failed CSSFontFaceSource from CSSFontFace

If a CSSFontFaceSource failed to generate valid font data, there is no
reason to keep it. This also makes isValid() constant-time.

BUG=
TEST=covered by existing tests

Review URL: https://codereview.chromium.org/141513010

git-svn-id: svn://svn.chromium.org/blink/trunk@166283 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Mark http/tests/appcache/online-whitelist.html flaky.

BUG=268111
TBR=caseq@chromium.org

Review URL: https://codereview.chromium.org/135153006

git-svn-id: svn://svn.chromium.org/blink/trunk@166284 bbb929c8-8fbe-4397-9dbb-9b2b20218538
IDL compiler: sync Python to r166277

Python side to:
Pass an Isolate around in context related methods
https://codereview.chromium.org/151283002

BUG=239771
TBR=haraken
NOTRY=true

Review URL: https://codereview.chromium.org/134623010

git-svn-id: svn://svn.chromium.org/blink/trunk@166285 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Widen expectations for flaky virtual/threaded/transitions/ tests

The following have been failing on Linux for a few weeks:
virtual/threaded/transitions/transition-end-event-set-none.html
virtual/threaded/transitions/transition-end-event-multiple-02.html

BUG=248938
TBR=caseq

Review URL: https://codereview.chromium.org/133533009

git-svn-id: svn://svn.chromium.org/blink/trunk@166286 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[Font Load Events] Update FontFaceSet status when added/removed FontFace while loading

This patch tells FontFaceSet to adjust m_loadingCount when a FontFace is
added or removed while its status is "loading".

BUG=53213
TEST=fast/css/fontfaceset-add-remove-while-loading.html

Review URL: https://codereview.chromium.org/147953003

git-svn-id: svn://svn.chromium.org/blink/trunk@166287 bbb929c8-8fbe-4397-9dbb-9b2b20218538