Disabled instrumentation in writing scopes.

Author: N. Taylor Mullen

src/Microsoft.AspNet.Razor/Generator/Compiler/CodeBuilder/CSharp/CSharpTagHelperCodeRenderer.cs

@@ -409,6 +409,11 @@ private void BuildBufferedWritingScope(IList<Chunk> chunks)
             // ensure we capture all content that's written, directly or indirectly.
             var oldWriter = _context.TargetWriterName;
             _context.TargetWriterName = null;
+            
+            // Need to disable instrumentation inside of writing scopes, the instrumentation will not detect
+            // content written inside writing scopes.
+            var oldInstrumentation = _context.Host.EnableInstrumentation;
+            _context.Host.EnableInstrumentation = false;
 
             _writer.WriteMethodInvocation(_tagHelperContext.StartWritingScopeMethodName);
 
@@ -417,6 +422,9 @@ private void BuildBufferedWritingScope(IList<Chunk> chunks)
             _writer.WriteStartAssignment(StringValueBufferVariableName)
                    .WriteMethodInvocation(_tagHelperContext.EndWritingScopeMethodName);
 
+            // Restore the instrumentation
+            _context.Host.EnableInstrumentation = oldInstrumentation;
+
             // Reset the writer/buffer back to what it was, no longer in a writing scope.
             _context.TargetWriterName = oldWriter;
         }