Should check whether document.settings() is available or not when updating GenericFontFamilySetting…

Source/core/dom/StyleEngine.cpp

Index: Source/core/dom/StyleEngine.cpp
diff --git a/Source/core/dom/StyleEngine.cpp b/Source/core/dom/StyleEngine.cpp
index 4d1a0b46a5f9118dbc190a660ca1dd11fa76466b..ab1d4defb1ef174763a63212c543d5c58bbc352b 100644
--- a/Source/core/dom/StyleEngine.cpp
+++ b/Source/core/dom/StyleEngine.cpp
@@ -531,6 +531,8 @@ void StyleEngine::clearFontCache()
 
 void StyleEngine::updateGenericFontFamilySettings()
 {
+    if (!document().isActive() || !document().settings())

[dglazkov, 2014/05/29 22:24:28]

Just checking: is this a symptom of a larger problem? Is it ok for
WebSettingsImpl to call this on a frameless doc?

[tasak, 2014/05/30 02:12:05]

As far as I investigated,

WebSettingsImpl::setStandardFontFamily (i.e. m_settings != null)
 ==> Settings::notifyGenericFontFamilyChange()
 ==> Page::settingsChanged()
    (obtain StyleEngine instance by using mainFrame() and frame->document() and
document()->styleEngine())
 ==> StyleEngine::updateGenericFontFamilySettings()

Looking at Document::settings(),
 - m_frame->settings() used in Document::settings
 - m_host->settings() used in Frame::settings()
 - m_page->settings() used in FrameHost::settings()
 - Page has OwnPtr<Settings> (strictly speaking, SettingsDelegate owns.)

I think,
  - Page has non-null m_settings, because Page creates Settings in its
constructor (i.e. SettingsDelegate(Settings::create()) )
  - FrameHost also has non-null m_page, because Page creates FrameHost in its
constructor. (i.e. m_frameHost(FrameHost::create(*this)) )
  - Document has non-null m_frame, because frame->document() seems to work.

So LocalFrame seems not to have m_host.

Talking about "it's ok or not", each settings() says "settings() can return
null". LocalFrame's constructor takes "FrameHost*" (not FrameHost&).

So this "no FrameHost localframe" would be expected (by someone who added the
comment).

+        return;
     if (!m_fontSelector)
         return;