[chromium] Remove WebLayer::setChildren API

[chromium] Remove WebLayer::setChildren API
https://bugs.webkit.org/show_bug.cgi?id=94749

Reviewed by Adrienne Walker.

Source/Platform:

This is redundant with removeAllChildren() / addChild() and less efficient.

* chromium/public/WebLayer.h:
(WebLayer):

Source/WebCore:

Sets up the child list directly instead of building an intermediate buffer. Covered by compositing/*

* platform/graphics/chromium/GraphicsLayerChromium.cpp:
(WebCore::GraphicsLayerChromium::updateChildList):

Source/WebKit/chromium:

* src/WebLayer.cpp:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@126498 268f45cc-cd09-0410-ab3c-d52691b4dbfc