Fix race condition in DecoratorAdaptableTests by adding event loop processing

[vogella]

Summary

Fixes #868

This PR fixes a race condition in DecoratorAdaptableTests that was causing intermittent test failures with the error:

"Adaptable test 1 has failed for object org.eclipse.ui.tests.menus.ObjectContributionClasses$A@..."

Problem

The tests were experiencing intermittent failures due to a race condition. After enabling decorators in the @Before method using setEnabled(), the decorator manager schedules asynchronous updates that may not have completed before the test assertions ran.

Solution

This PR applies the same pattern used to fix other race conditions in Eclipse UI tests (like the recent fix for MMenuItemTest in a988d08):

1. Added import for UITestUtil which provides event loop processing utilities
2. Added UITestUtil.processEvents() after decorator enablement in @Before to ensure all pending UI events are processed
3. Added UITestUtil.processEvents() in @After to ensure a clean state for subsequent tests

The processEvents() method processes all pending events in the Display event queue, ensuring that decorator registration and enablement updates have completed before the test proceeds.

Test Plan

• Successfully ran all 3 tests in DecoratorAdaptableTests:
  • testAdaptables
  • testNonAdaptableContributions
  • testContributorResourceAdapter
• Ran tests multiple times to verify consistency
• All tests passed with no failures or errors

Related Changes

This fix follows the same pattern as other recent race condition fixes in the repository.

🤖 Generated with Claude Code

[github-actions]

Test Results

 3 018 files  ±0   3 018 suites  ±0   2h 33m 17s ⏱️ + 17m 36s
 8 229 tests ±0   7 979 ✅  - 1  249 💤 ±0  1 ❌ +1 
23 607 runs  ±0  22 812 ✅  - 1  794 💤 ±0  1 ❌ +1 

For more details on these failures, see this check.

Results for commit a6c3eb8. ± Comparison against base commit 4acc3e3.