取得webview的內容size

https://stackoverflow.com/questions/3936041/how-to-determine-the-content-size-of-a-uiwebview

- (void)webViewDidFinishLoad:(UIWebView *)aWebView {
    CGRect frame = aWebView.frame;
    frame.size.height = 1;
    aWebView.frame = frame;
    CGSize fittingSize = [aWebView sizeThatFits:CGSizeZero];
    frame.size = fittingSize;
    aWebView.frame = frame;

    NSLog(@"size: %f, %f", fittingSize.width, fittingSize.height);
}

要先設height到很小，再做[webView sizeToFit]; 或 [webView sizeThatFits:CGSizeZero];