Fix race condition in DecoratorAdaptableTests by adding event loop processing

Fixes eclipse-platform#868

The tests testAdaptables, testNonAdaptableContributions, and
testContributorResourceAdapter were experiencing intermittent failures
due to a race condition. After enabling decorators in the @before method,
the decorator manager schedules asynchronous updates that may not have
completed before the test assertions ran.

This commit adds calls to UITestUtil.processEvents() in both @before
and @after methods to ensure all pending UI events are processed before
tests run and after tests complete. This is a standard pattern for
preventing race conditions in Eclipse UI 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.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: vogella

tests/org.eclipse.ui.tests/Eclipse UI Tests/org/eclipse/ui/tests/decorators/DecoratorAdaptableTests.java

@@ -25,6 +25,7 @@
 import org.eclipse.ui.internal.decorators.DecorationResult;
 import org.eclipse.ui.internal.decorators.DecoratorManager;
 import org.eclipse.ui.internal.decorators.LightweightDecoratorManager;
+import org.eclipse.ui.tests.harness.util.UITestUtil;
 import org.eclipse.ui.tests.menus.ObjectContributionClasses;
 import org.junit.After;
 import org.junit.Before;
@@ -63,6 +64,10 @@ public void doSetUp() throws Exception {
 		PlatformUI.getWorkbench().getDecoratorManager().setEnabled(TestUnadaptableDecoratorContributor.ID, true);
 		PlatformUI.getWorkbench().getDecoratorManager().setEnabled(TestResourceDecoratorContributor.ID, true);
 		PlatformUI.getWorkbench().getDecoratorManager().setEnabled(TestResourceMappingDecoratorContributor.ID, true);
+
+		// Process all pending UI events to ensure decorator enablement has completed
+		// This prevents race conditions where decorators may not be fully registered yet
+		UITestUtil.processEvents();
 	}
 
 	@After
@@ -71,6 +76,9 @@ public void doTearDown() throws Exception {
 		PlatformUI.getWorkbench().getDecoratorManager().setEnabled(TestUnadaptableDecoratorContributor.ID, false);
 		PlatformUI.getWorkbench().getDecoratorManager().setEnabled(TestResourceDecoratorContributor.ID, false);
 		PlatformUI.getWorkbench().getDecoratorManager().setEnabled(TestResourceMappingDecoratorContributor.ID, false);
+
+		// Process all pending UI events to ensure clean state for next test
+		UITestUtil.processEvents();
 	}
 
 	/**