Merge 86132 - 2011-05-10 MORITA Hajime <morrita@google.com>

Merge 86132 - 2011-05-10  MORITA Hajime  <morrita@google.com>;

        Reviewed by Ryosuke Niwa.

        REGRESSION(r73886): Frequent crashes in replaceSelectionWithFragment
        https://bugs.webkit.org/show_bug.cgi?id=60090

        SpellChecker uses TextCheckerClient, which belongs Page object,
        which is possibly destroyed during SpellChecker's lifetime.
        This change added to a guard before using TextCheckerClient to
        ensure it being live.

        No new tests, this is a speculative fix for a real crash.

        * editing/Editor.cpp:
        (WebCore::Editor::Editor):
        * editing/SpellChecker.cpp:
        (WebCore::SpellChecker::SpellChecker):
        (WebCore::SpellChecker::client):
        (WebCore::SpellChecker::canCheckAsynchronously):
        (WebCore::SpellChecker::requestCheckingFor):
        * editing/SpellChecker.h:

TBR=levin@chromium.org
BUG=82238
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=86212