Check known file extensions for icons when collecting usage data.

Check the file extension against file filters first and then
check the file extensions that have an associated icon.

src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/AvalonEditViewContent.cs

@@ -41,7 +41,7 @@ namespace ICSharpCode.AvalonEdit.AddIn
 			
 			if (file.FileName != null) {
 				string filetype = Path.GetExtension(file.FileName);
-				if (!ProjectService.GetFileFilters().Any(f => f.ContainsExtension(filetype)))
+				if (!IsKnownFileExtension(filetype))
 					filetype = ".?";
 				trackedFeature = AnalyticsMonitorService.TrackFeature(typeof(AvalonEditViewContent), "open" + filetype.ToLowerInvariant());
 			}
@@ -55,6 +55,12 @@ namespace ICSharpCode.AvalonEdit.AddIn
 			codeEditor.TextCopied += codeEditor_TextCopied;
 		}
 		
+		bool IsKnownFileExtension(string filetype)
+		{
+			return ProjectService.GetFileFilters().Any(f => f.ContainsExtension(filetype)) ||
+				IconService.HasImageForFile(filetype);
+		}
+		
 		void codeEditor_Document_UndoStack_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
 		{
 			if (!isLoading)

src/Main/Base/Project/Src/Services/IconService.cs

@@ -102,6 +102,12 @@ namespace ICSharpCode.SharpDevelop
 			return "Icons.16x16.MiscFiles";
 		}
 		
+		public static bool HasImageForFile(string fileName)
+		{
+			string extension = Path.GetExtension(fileName).ToUpperInvariant();
+			return extensionHashtable.ContainsKey(extension);
+		}
+		
 		static void InitializeIcons(AddInTreeNode treeNode)
 		{
 			extensionHashtable[".PRJX"] = "Icons.16x16.SolutionIcon";