[Cherry-pick] [CoordinatedGraphics] Crash at CoordinatedGraphicsScene::updateImageBacking

[CoordinatedGraphics] Crash at CoordinatedGraphicsScene::updateImageBacking
https://bugs.webkit.org/show_bug.cgi?id=118613

The operations of creating/removing/updating/clearing weren't in the
right sequence. Changing the order solves the issue because when an image is
replaced the old one is deleted before the new one is created, and IDs are
not unique in cairo (they're based on the image pointer).

Reviewed by Noam Rosenthal.

* platform/graphics/texmap/coordinated/CoordinatedGraphicsScene.cpp:
(WebCore::CoordinatedGraphicsScene::syncImageBackings):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@152647 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Conflicts:

	Source/WebCore/ChangeLog