Reviewed by John Sullivan.

    Reviewed by John Sullivan.

        <rdar://problem/4494340> REGRESSION: Making the font size bigger/smaller in an HTML message doesn't affect the body until you reopen it

        Problem was the public API -[WebView setTextSizeMultiplier] did not notify anyone that the value changed.

        * WebView/WebDocumentInternal.h:
        Add _textSizeMultiplierChanged to the _WebDocumentTextSizing protocol.

        * WebView/WebHTMLView.m:
        (-[WebHTMLView _textSizeMultiplierChanged]):
        Send [self _updateTextSizeMultiplier].

        * WebView/WebPDFView.m:
        (-[WebPDFView _textSizeMultiplierChanged]):
        ASSERT_NOT_REACHED() because WebPDFView does not track the common multiplier.

        * WebView/WebView.m:
        (-[WebView setTextSizeMultiplier:]):
        Send [self _notifyTextSizeMultiplierChanged];

        (-[WebView _performTextSizingSelector:withObject:onTrackingDocs:selForNonTrackingDocs:newScaleFactor:]):
        Alter the _textSizeMultiplier directly so that notification is not sent.
        Minor formatting.

        (-[WebView _notifyTextSizeMultiplierChanged]):
        New. Send _textSizeMultiplierChanged to all document views that track the common multiplier.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@16437 268f45cc-cd09-0410-ab3c-d52691b4dbfc