Decrease latency before cancellation when multiple threads asking for checkCancelled concurrently.

platform/platform-api/src/com/intellij/openapi/progress/ProgressManager.java

@@ -43,8 +43,8 @@ public abstract class ProgressManager {
   public static void checkCanceled() throws ProcessCanceledException {
     // smart optimization! There's a thread started in ProgressManagerImpl, that set's this flag up once in 10 milliseconds
     if (ourNeedToCheckCancel) {
-      ourNeedToCheckCancel = false;
       getInstance().doCheckCanceled();
+      ourNeedToCheckCancel = false;
     }
   }
 

platform/platform-impl/src/com/intellij/openapi/progress/impl/ProgressManagerImpl.java

@@ -85,7 +85,7 @@ public class ProgressManagerImpl extends ProgressManager {
         }
         else {
           ourLockedCheckCounter = 0;
-          progress.checkCanceled();
+          throw e;
         }
       }
     }