Bug 491417: fix occasional "..." updates in disassembly

When a viewportChanged event and a setActive event arrived at the same
following a debug context change the two event handlers would cancel
each other out.

Change-Id: I07a8d0ff46e4ea4f4ab682a5311650fca021d75b
Signed-off-by: Jonah Graham <jonah@kichwacoders.com>
diff --git a/dsf/org.eclipse.cdt.dsf.ui/src/org/eclipse/cdt/dsf/debug/internal/ui/disassembly/DisassemblyPart.java b/dsf/org.eclipse.cdt.dsf.ui/src/org/eclipse/cdt/dsf/debug/internal/ui/disassembly/DisassemblyPart.java
index 83c2f2c..6f154c6 100644
--- a/dsf/org.eclipse.cdt.dsf.ui/src/org/eclipse/cdt/dsf/debug/internal/ui/disassembly/DisassemblyPart.java
+++ b/dsf/org.eclipse.cdt.dsf.ui/src/org/eclipse/cdt/dsf/debug/internal/ui/disassembly/DisassemblyPart.java
@@ -1495,7 +1495,8 @@
 	 */
 	@Override
 	public void viewportChanged(int verticalOffset) {
-		if (fDebugSessionId != null && fGotoAddressPending == PC_UNKNOWN && fScrollPos == null && !fUpdatePending && !fRefreshViewPending) {
+		if (fDebugSessionId != null && fGotoAddressPending == PC_UNKNOWN && fScrollPos == null && !fUpdatePending && !fRefreshViewPending 
+				&& fFocusAddress != PC_UNKNOWN) {
 			fUpdatePending = true;
             final int updateCount = fUpdateCount;
             invokeLater(new Runnable() {