Assertion failure in GlyphPage::setGlyphDataForIndex: (!glyph || fontData == m_fontDataForAllGlyphs)
<http://webkit.org/b/116113>
<rdar://problem/13833790>

Reviewed by Dan Bernstein.

If we're filling a full GlyphPage with a SimpleFontData that is actually a composite font reference,
we need to make sure we have per-glyph font data pointers, since it may end up using them.

Added GlyphPage::mayUseMixedFontDataWhenFilling() which can be implemented by the platform to let
GlyphPageTreeNode know that it should allocate a full-sized GlyphPage for mixed font data pointers
in case the font is a composite font reference, or if there are CJK ideographs in the text.

This code can be made smarter, but that's outside the scope of this change.
Fixes heavy asserting on bots running unreleased software.

* platform/graphics/GlyphPage.h:
(GlyphPage):
(WebCore::GlyphPage::mayUseMixedFontDataWhenFilling):
* platform/graphics/GlyphPageTreeNode.cpp:
(WebCore::GlyphPageTreeNode::initializePage):
* platform/graphics/mac/GlyphPageTreeNodeMac.cpp:
(WebCore::shouldUseCoreText):
(WebCore::GlyphPage::mayUseMixedFontDataWhenFilling):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@150085 268f45cc-cd09-0410-ab3c-d52691b4dbfc