Provide a timeout for query that might run in UI thread.

GdbReverseToggleCommand extends AbstractDebugCommand so as to be able to
block without risking a deadlock.  However, this only applies to
doExecute() and isExecutable().

GdbReverseToggleCommand has two other methods that use queries, and
those are at risk of a deadlock: isReverseToggled() and
getReverseDebugMethod().  Those queries must have a timeout to avoid any
risk of deadlock.

Change-Id: Ia410b8f102638965ccbf8ac9deda06dc4efc5f0d

dsf-gdb/org.eclipse.cdt.dsf.gdb.ui/src/org/eclipse/cdt/dsf/gdb/internal/ui/commands/GdbReverseToggleCommand.java

@@ -279,12 +279,15 @@ public class GdbReverseToggleCommand extends AbstractDebugCommand implements ICh
     	};
     	try {
     		fExecutor.execute(isToggledQuery);
-    		return isToggledQuery.get();
+    		return isToggledQuery.get(500, TimeUnit.MILLISECONDS);
     	} catch (InterruptedException e) {
     	} catch (ExecutionException e) {
     	} catch (RejectedExecutionException e) {
     		// Can be thrown if the session is shutdown
-    	}
+        } catch (TimeoutException e) {
+        	// If we timeout, we default to false.
+        	// This is to avoid a deadlock
+        }
 
     	return false;
     }
@@ -390,6 +393,8 @@ public class GdbReverseToggleCommand extends AbstractDebugCommand implements ICh
         } catch (ExecutionException e) {
         } catch (RejectedExecutionException e) {
         } catch (TimeoutException e) {
+        	// If we timeout, we default to OFF.
+        	// This is to avoid a deadlock
         }
 
         return ReverseDebugMethod.OFF;