Bug 96917 [implementation] If two editors use the 2.x-compatible API, one or both doesn't work
At least one problem is that 3.0 installs partitioners for every editor that might possibly edit a file, but each editor expects its own partitioner to be installed. Leading to the famous white screen with blue line.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/CompilationUnitDocumentProvider.java
* Sets up the infrastructure necessary for problem reporting.
			 *
			 * @param insideReportingSequence <code>true</code> if this method
			 *            call is issued from inside a reporting sequence
			 */
			private void internalBeginReporting(boolean insideReportingSequence) {
				if (fCompilationUnit != null && fCompilationUnit.getJavaProject().isOnClasspath(fCompilationUnit)) {
					ProblemRequestorState state= new ProblemRequestorState();
					state.fInsideReportingSequence= insideReportingSequence;
					state.fReportedProblems= new ArrayList();
					synchronized (getLockObject()) {
						fProblemRequestorState.set(state);
						++fStateCount;
					}
				}
			}
			/*
			 * @see IProblemRequestor#acceptProblem(IProblem)
			 */
			public void acceptProblem(IProblem problem) {
				if (fIsHandlingTemporaryProblems) {
					ProblemRequestorState state= (ProblemRequestorState) fProblemRequestorState.get();
					if (state != null)
						state.fReportedProblems.add(problem);
				}
			}
			/*
			 * @see IProblemRequestor#endReporting()
			 */
			public void endReporting() {