Add GetDispatcherFromFileName to unify trace loading

Added a static method to decide which trace event dispatcher to use when
loading a trace file.

src/EtwHeapDump/DotNetHeapDumpGraphReader.cs

@@ -49,16 +49,8 @@ public class DotNetHeapDumpGraphReader
 	}
     public void Append(MemoryGraph memoryGraph, string etlName, string processNameOrId = null, double startTimeRelativeMSec = 0)
     {
-        if (etlName.EndsWith(".trace.zip", StringComparison.OrdinalIgnoreCase))
-        {
-            using (var source = new CtfTraceEventSource(etlName))
-                Append(memoryGraph, source, processNameOrId, startTimeRelativeMSec);
-        }
-        else
-        {
-            using (var source = new ETWTraceEventSource(etlName))
-                Append(memoryGraph, source, processNameOrId, startTimeRelativeMSec);
-        }
+        using (var source = TraceEventDispatcher.GetDispatcherFromFileName(etlName))
+            Append(memoryGraph, source, processNameOrId, startTimeRelativeMSec);
     }
     public void Append(MemoryGraph memoryGraph, TraceEventDispatcher source, string processNameOrId = null, double startTimeRelativeMSec = 0)
     {

src/PerfView/Extensibility.cs

@@ -2263,8 +2263,7 @@ namespace PerfViewExtensibility
             if (gcDumpOutputFileName == null)
                 gcDumpOutputFileName = PerfViewFile.ChangeExtension(etlFileName, ".gcdump");
 
-            if (!etlFileName.EndsWith(".trace.zip", StringComparison.OrdinalIgnoreCase))
-                ETLPerfViewData.UnZipIfNecessary(ref etlFileName, LogFile);
+            ETLPerfViewData.UnZipIfNecessary(ref etlFileName, LogFile);
 
             // TODO FIX NOW retrieve the process name, ID etc.  
             var reader = new DotNetHeapDumpGraphReader(LogFile);
@@ -2962,7 +2961,7 @@ namespace PerfViewExtensibility
         {
             ETLPerfViewData.UnZipIfNecessary(ref etlFile, LogFile);
 
-            var source = new ETWTraceEventSource(etlFile);
+            var source = TraceEventDispatcher.GetDispatcherFromFileName(etlFile);
             var gcStats = Stats.GCProcess.Collect(source, 1);   // TODO we don't know that it is 1 msec sampling.  
 
             var outputFileName = Path.ChangeExtension(etlFile, ".gcStats.html");
@@ -3014,7 +3013,7 @@ namespace PerfViewExtensibility
         {
             ETLPerfViewData.UnZipIfNecessary(ref etlFile, LogFile);
 
-            var source = new ETWTraceEventSource(etlFile);
+            var source = TraceEventDispatcher.GetDispatcherFromFileName(etlFile);
             var jitStats = Stats.JitProcess.Collect(source);
 
             var outputFileName = Path.ChangeExtension(etlFile, ".jitStats.html");

src/PerfView/PerfViewData.cs

@@ -5209,6 +5209,12 @@ namespace PerfView
 
         internal static void UnZipIfNecessary(ref string inputFileName, TextWriter log, bool unpackInCache = true, bool wprConventions = false)
         {
+            if (inputFileName.EndsWith(".trace.zip", StringComparison.OrdinalIgnoreCase))
+            {
+                log.WriteLine($"'{inputFileName}' is a linux trace.");
+                return;
+            }
+
             var extension = Path.GetExtension(inputFileName);
             if (string.Compare(extension, ".zip", StringComparison.OrdinalIgnoreCase) == 0 ||
                 string.Compare(extension, ".vspx", StringComparison.OrdinalIgnoreCase) == 0)

src/TraceEvent/TraceEvent.cs

@@ -2661,6 +2661,20 @@ namespace Microsoft.Diagnostics.Tracing
     /// </summary>
     abstract unsafe public class TraceEventDispatcher : TraceEventSource
     {
+        /// <summary>
+        /// Obtains the correct TraceEventDispatcher for the given trace file name.
+        /// </summary>
+        /// <param name="traceFileName">A path to a trace file.</param>
+        /// <returns>A TraceEventDispatcher for the given trace file.</returns>
+        public static TraceEventDispatcher GetDispatcherFromFileName(string traceFileName)
+        {
+            if (traceFileName.EndsWith(".trace.zip", StringComparison.OrdinalIgnoreCase) ||
+                traceFileName.EndsWith(".lttng.zip", StringComparison.OrdinalIgnoreCase))
+                return new CtfTraceEventSource(traceFileName);
+            else
+                return new ETWTraceEventSource(traceFileName);
+        }
+
         // Normally you subscribe to events using parsers that 'attach' themselves to the source. However
         // there are a couple of events that TraceEventDispatcher can handle directly.
         /// <summary>

src/TraceEvent/TraceLog.cs

@@ -59,7 +59,7 @@ namespace Microsoft.Diagnostics.Tracing.Etlx
         {
             if (etlxFilePath == null)
                 etlxFilePath = Path.ChangeExtension(filePath, ".etlx");
-            using (TraceEventDispatcher source = GetDispatcherFromFileName(filePath))
+            using (TraceEventDispatcher source = TraceEventDispatcher.GetDispatcherFromFileName(filePath))
             {
                 if (source.EventsLost != 0 && options != null && options.OnLostEvents != null)
                     options.OnLostEvents(false, source.EventsLost, 0);
@@ -590,16 +590,6 @@ namespace Microsoft.Diagnostics.Tracing.Etlx
             }
         }
 
-		private static TraceEventDispatcher GetDispatcherFromFileName(string filePath)
-		{
-			if (filePath.EndsWith(".trace.zip"))
-			{
-				return new CtfTraceEventSource(filePath);
-			}
-
-			return new ETWTraceEventSource(filePath);
-		}
-
 		/// <summary>
 		/// Given a process's virtual address 'address' and an event which acts as a 
 		/// context (determines which process and what time in that process), return