Bug 1142197 - manage ProfilerBacktrace with UniquePtr; r=mstange

Smart pointers are better than raw pointers.

xpcom/build/MainThreadIOLogger.cpp

@@ -172,12 +172,8 @@ MainThreadIOLoggerImpl::IOThreadFunc()
                        (i->mObservation.Start() - mLogStartTime).ToMilliseconds(),
                        i->mObservation.ObservedOperationString(), durationMs,
                        i->mObservation.Reference(), nativeFilename.get()) > 0) {
-          ProfilerBacktrace* stack = i->mStack;
-          if (stack) {
-            // TODO: Write out the callstack
-            //       (This will be added in a later bug)
-            profiler_free_backtrace(stack);
-          }
+          // TODO: Write out the callstack
+          i->mStack = nullptr;
         }
       }
     }