#Java, (削除) 404 (削除ここまで)(削除) 388 (削除ここまで)(削除) 354 (削除ここまで)(削除) 348 (削除ここまで)(削除) 320 (削除ここまで) 318 bytes

Java, (削除) 404 (削除ここまで)(削除) 388 (削除ここまで)(削除) 354 (削除ここまで)(削除) 348 (削除ここまで)(削除) 320 (削除ここまで) 318 bytes

#Java, (削除) 404 (削除ここまで) (削除) 388 (削除ここまで) (削除) 354 (削除ここまで) (削除) 348 (削除ここまで) 320 bytes

import java.awt.*;import java.awt.event.*;interface M{static void main(String[]a){new Frame(){{add(new TextArea(){{addKeyListener(new KeyAdapter(){long t,i=96;public void keyPressed(KeyEvent e){t=t>0?t:e.getWhen();if(e.getKeyChar()!=++i|i>121){System.out.print(i>121?e.getWhen()-t:"Fail");dispose();}}});}});show();}};}}

import java.awt.*; // Required import for Frame and TextField
import java.awt.event.*; // Required import for KeyAdapter and KeyEvent
interface M{ // Class
 static void main(String[]a){ // Mandatory main-method
 new Frame(){ // Create the GUI-Frame
 { // With an initialization-block
 add(new TextArea(){ // Add an input-field
 { // With it's own initialization-block
 addKeyListener(new KeyAdapter(){
 // Add a KeyAdapter to the input-field
 long t, // Long to save the time
 i=96; // Previous character, starting at 96 ('a'-1)
 public void keyPressed(KeyEvent e){ 
 // Override the keyPressed-method:
 t=t>0? // If `t` is already set:
 t // Leave it the same
 : // Else:
 e.getWhen(); // Save the current time (== start the timer)
 if(e.getKeyChar()!=++i
 // As soon as an incorrect character is pressed,
 |i>121){ // or we've reached 'z':
 System.out.print(i>121?
 // If we're at 'z':
 e.getWhen()-t // Print the end-time in ms to the Console
 : // Else (an incorrect character was pressed)
 "Fail"); // Print "Fail" to the Console
 dispose();} // And exit the application
 } // End of keyPressed-method
 }); // End of KeyAdapter
 } // End of input-field initialization-block
 }); // End of input-field
 show(); // Initially show the Frame
 } // End of Frame initialization-block
 } // End of Frame 
 } // End of main-method
} // End of class

#Java, (削除) 404 (削除ここまで) (削除) 388 (削除ここまで) (削除) 354 (削除ここまで) (削除) 348 (削除ここまで) (削除) 320 (削除ここまで) 318 bytes

import java.awt.*;import java.awt.event.*;interface M{static void main(String[]a){new Frame(){{add(new TextArea(){{addKeyListener(new KeyAdapter(){long t,i=64;public void keyPressed(KeyEvent e){t=t>0?t:e.getWhen();if(e.getKeyChar()!=++i|i>89){System.out.print(i>89?e.getWhen()-t:"Fail");dispose();}}});}});show();}};}}

import java.awt.*; // Required import for Frame and TextField
import java.awt.event.*; // Required import for KeyAdapter and KeyEvent
interface M{ // Class
 static void main(String[]a){ // Mandatory main-method
 new Frame(){ // Create the GUI-Frame
 { // With an initialization-block
 add(new TextArea(){ // Add an input-field
 { // With it's own initialization-block
 addKeyListener(new KeyAdapter(){
 // Add a KeyAdapter to the input-field
 long t, // Long to save the time
 i=64; // Previous character, starting at code of 'a'-1
 public void keyPressed(KeyEvent e){ 
 // Override the keyPressed-method:
 t=t>0? // If `t` is already set:
 t // Leave it the same
 : // Else:
 e.getWhen(); // Save the current time (== start the timer)
 if(e.getKeyCode()!=++i
 // As soon as an incorrect character is pressed,
 |i>89){ // or we've reached 'z':
 System.out.print(i>89?
 // If we're at 'z':
 e.getWhen()-t // Print the end-time in ms to the Console
 : // Else (an incorrect character was pressed)
 "Fail"); // Print "Fail" to the Console
 dispose();} // And exit the application
 } // End of keyPressed-method
 }); // End of KeyAdapter
 } // End of input-field initialization-block
 }); // End of input-field
 show(); // Initially show the Frame
 } // End of Frame initialization-block
 }; // End of Frame 
 } // End of main-method
} // End of class

#Java, (削除) 404 (削除ここまで) (削除) 388 (削除ここまで) (削除) 354 (削除ここまで) 348 bytes

import java.awt.*;import java.awt.event.*;class M extends Frame{{TextArea f=new TextArea();add(f);f.addKeyListener(new KeyAdapter(){long t,i=96,c;public void keyPressed(KeyEvent e){t=t>0?t:e.getWhen();c=e.getKeyChar();if(c!=++i|i>121){System.out.print(i>121?e.getWhen()-t:"Fail");dispose();}}});show();}public static void main(String[]a){new M();}}

-50 bytes thanks to @OlivierGrégoire.

import java.awt.*; // Required import for Frame and TextField
import java.awt.event.*; // Required import for KeyAdapter and KeyEvent
class M extends Frame{ // Class (extending Frame)
 { // Class-initialization
 TextArea f=new TextArea () // Instantiate an input-field
 add(f); // Add the input-field to the Frame
 f.addKeyListener(new KeyAdapter(){
 // Add a KeyAdapter to the input-field
 long t, // Long to save the time
 i=96, // Previous character, starting at 96 ('a'-1)
 c;  // Current character
 public void keyPressed(KeyEvent e){ 
 // Override the keyPressed-method:
 t=t>0? // If `t` is already set:
 t // Leave it the same
 : // Else:
 e.getWhen(); // Save the current time (== start the timer)
 c=e.getKeyChar(); // Get the character pressed by the user
 if(c!=++i // As soon as an incorrect character is pressed,
 |i>121){ // or we've reached 'z':
 System.out.print(i>121? // If we're at 'z':
 e.getWhen()-t //  Print the end-time in ms to the Console
 : // Else (an incorrect character was pressed)
 "Fail")); // Print "Fail" to the Console
 dispose();} // And exit the application
 } // End of keyPressed-method
 }); // End of KeyAdapter
 show(); // Initially show the Frame
 } // End of class-initialization
 public static void main(String[]a){ // Mandatory main-method
 new M(); // Create an instance of itself (of the Frame)
 } // End of main-method
} // End of class

#Java, (削除) 404 (削除ここまで) (削除) 388 (削除ここまで) (削除) 354 (削除ここまで) (削除) 348 (削除ここまで) 320 bytes

import java.awt.*;import java.awt.event.*;interface M{static void main(String[]a){new Frame(){{add(new TextArea(){{addKeyListener(new KeyAdapter(){long t,i=96;public void keyPressed(KeyEvent e){t=t>0?t:e.getWhen();if(e.getKeyChar()!=++i|i>121){System.out.print(i>121?e.getWhen()-t:"Fail");dispose();}}});}});show();}};}}

-78 bytes thanks to @OlivierGrégoire.

import java.awt.*; // Required import for Frame and TextField
import java.awt.event.*; // Required import for KeyAdapter and KeyEvent
interface M{ // Class static void main(String[]a){ // Mandatory main-method
  new Frame(){ // Create the GUI-Frame
 { //  With an initialization-block
 add(new TextArea(){  // Add an input-field
 {  // With it's own initialization-block
 addKeyListener(new KeyAdapter(){
 // Add a KeyAdapter to the input-field
 long t, // Long to save the time
 i=96; // Previous character, starting at 96 ('a'-1)
 public void keyPressed(KeyEvent e){ 
 // Override the keyPressed-method:
 t=t>0? // If `t` is already set:
 t // Leave it the same
 : // Else:
 e.getWhen(); // Save the current time (== start the timer)
 if(e.getKeyChar()!=++i
 // As soon as an incorrect character is pressed,
 |i>121){ // or we've reached 'z':
 System.out.print(i>121? // If we're at 'z':
 e.getWhen()-t // Print the end-time in ms to the Console
 : // Else (an incorrect character was pressed)
 "Fail"); // Print "Fail" to the Console
 dispose();} // And exit the application
 } // End of keyPressed-method
 }); // End of KeyAdapter
 }  // End of input-field initialization-block
  }); // End of input-field
  show(); // Initially show the Frame
 } //  End of Frame initialization-block
 } // End of Frame
 } // End of main-method
} // End of class