Don't change Document load progress in any page dismissal events.

This can confuse the logic for blocking modal dialogs.

BUG=536652

Review URL: https://codereview.chromium.org/1373113002

Cr-Commit-Position: refs/heads/master@{#351419}
bool Document::execCommand(const String& commandName, bool, const String& value, ExceptionState& exceptionState)
{
    if (!isHTMLDocument() && !isXHTMLDocument()) {
        exceptionState.throwDOMException(InvalidStateError, "execCommand is only supported on HTML documents.");
        return false;
    }

    static bool inExecCommand = false;
    if (inExecCommand) {
        String message = "We don't execute document.execCommand() this time, because it is called recursively.";
        addConsoleMessage(ConsoleMessage::create(JSMessageSource, WarningMessageLevel, message));
        return false;
    }
    TemporaryChange<bool> executeScope(inExecCommand, true);

    EventQueueScope eventQueueScope;
    Editor::Command editorCommand = command(this, commandName);
    Platform::current()->histogramSparse("WebCore.Document.execCommand", editorCommand.idForHistogram());
    return editorCommand.execute(value);
}

bool Document::execCommand(const String& commandName, bool, const String& value, ExceptionState& exceptionState)
{
    if (!isHTMLDocument() && !isXHTMLDocument()) {
        exceptionState.throwDOMException(InvalidStateError, "execCommand is only supported on HTML documents.");
        return false;
    }

    static bool inExecCommand = false;
    if (inExecCommand) {
        String message = "We don't execute document.execCommand() this time, because it is called recursively.";
        addConsoleMessage(ConsoleMessage::create(JSMessageSource, WarningMessageLevel, message));
        return false;
    }
    TemporaryChange<bool> executeScope(inExecCommand, true);

    EventQueueScope eventQueueScope;
    Editor::Command editorCommand = command(this, commandName);
    Platform::current()->histogramSparse("WebCore.Document.execCommand", editorCommand.idForHistogram());
    return editorCommand.execute(value);
}
