Bug 326177 EPartService's getActivePart() does not appear to work properly for an application with multiple windows
Based on the code in PartServiceCreationFunction, the EPartService implementation being returned when an application's context is queried seems to be a window-level EPartService implementation.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
public int getActivated() {
			return activated;
		}
		public int getDeactivated() {
			return deactivated;
		}
		public int getHidden() {
			return hidden;
		}
		public int getVisible() {
			return visible;
		}
		public boolean isValid() {
			return valid;
		}
		public List<MPart> getActivatedParts() {
			return activatedParts;
		}
		public List<MPart> getDeactivatedParts() {
			return deactivatedParts;
		}
		public List<MPart> getHiddenParts() {
			return hiddenParts;
		}
		public List<MPart> getVisibleParts() {
			return visibleParts;
		}
		public void partActivated(MPart part) {
			if (valid && part == null) {
				valid = false;