Filter was modifying self in request. Fixed.

Filters are not allowed to call functions that call their MTime
to update during any request passes. vtkParticleTracerBase was
calling a Set method that did that. Fixed.

Change-Id: I2381c8400eff3d6a081df796ca5726fc89d75a96

Filters/FlowPaths/vtkParticleTracerBase.cxx

@@ -256,11 +256,11 @@ int vtkParticleTracerBase::RequestInformation(
     //clamp the default start time to be within the data time range
     if(this->StartTime < this->InputTimeValues[0])
       {
-      this->SetStartTime(this->InputTimeValues[0]);
+      this->StartTime = this->InputTimeValues[0];
       }
     else if (this->StartTime > this->InputTimeValues.back())
       {
-      this->SetStartTime(this->InputTimeValues.back());
+      this->StartTime = this->InputTimeValues.back();
       }
     }
   else
@@ -323,7 +323,7 @@ int vtkParticleTracerBase::RequestUpdateExtent(
       {
       double terminationTime = outInfo->Get(vtkStreamingDemandDrivenPipeline::UPDATE_TIME_STEP());
       PRINT("Pipeline has set termination time: "<< terminationTime);
-      this->SetTerminationTime(terminationTime);
+      this->SetTerminationTimeNoModify(terminationTime);
       }
 
     if(this->TerminationTime> this->InputTimeValues.back())
@@ -999,6 +999,8 @@ vtkPolyData* vtkParticleTracerBase::Execute(vtkInformationVector** inputVector)
   //Check post condition
   // To do:  verify here that the particles in ParticleHistories are consistent with CurrentTime
 
+  // These hold reference to the inputs. Release them.
+  this->DataReferenceT[0] = this->DataReferenceT[1] = 0;
   return output;
 }
 
@@ -1397,11 +1399,11 @@ void vtkParticleTracerBase::ResetCache()
 }
 
 //---------------------------------------------------------------------------
-void vtkParticleTracerBase::SetTerminationTime(double t)
+bool vtkParticleTracerBase::SetTerminationTimeNoModify(double t)
 {
   if(t==this->TerminationTime)
     {
-    return;
+    return false;
     }
 
   if (t < this->TerminationTime)
@@ -1415,8 +1417,18 @@ void vtkParticleTracerBase::SetTerminationTime(double t)
     t = this->StartTime;
     }
 
-  this->Modified();
   this->TerminationTime = t;
+
+  return true;
+}
+
+//---------------------------------------------------------------------------
+void vtkParticleTracerBase::SetTerminationTime(double t)
+{
+  if (this->SetTerminationTimeNoModify(t))
+    {
+    this->Modified();
+    }
 }
 
 //---------------------------------------------------------------------------

Filters/FlowPaths/vtkParticleTracerBase.h

@@ -412,6 +412,8 @@ private:
   bool RetryWithPush(
     vtkParticleTracerBaseNamespace::ParticleInformation &info, double* point1,double delT, int subSteps);
 
+  bool SetTerminationTimeNoModify(double t);
+
   //Parameters of tracing
   vtkInitialValueProblemSolver* Integrator;
   double IntegrationStep;