Bug 250604 [FieldAssist] API - ContentProposalAdapter needs isShowing() method
Please implement a method ContentProposalAdapter.isShwoing(). The method should return a boolean whether the content assistant proposal popup is open or not.
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/ContentProposalAdapter.java
* delay.
	 */
	private void autoActivate() {
		if (autoActivationDelay > 0) {
			Runnable runnable = new Runnable() {
				public void run() {
					receivedKeyDown = false;
					try {
						Thread.sleep(autoActivationDelay);
					} catch (InterruptedException e) {
					}
					if (!isValid() || receivedKeyDown) {
						return;
					}
					getControl().getDisplay().syncExec(new Runnable() {
						public void run() {
							openProposalPopup(true);
						}
					});
				}
			};
			Thread t = new Thread(runnable);
			t.start();
		} else {