With out using any plugins you can actually change the User-Agent in chrome browser by following the below steps.
Step 1: Open Developer Tools
Click on Settings (Located at top right corner) and click More Tools and then check Developer Tools
Step 2: Open Network Conditions
Click on settings which is located at top right corner of console and click More Tools and then click Network Conditions.
Step 3: Uncheck the 'Select Automatically' option
In Network Conditions under User Agent section, uncheck the Select Automatically option
Step 4: Now choose from the default list of User Agents or Paste your own User Agent String
Now you can choose any User Agent from existing list of User Agents or if you are looking for any specific User Agent string you can also paste that string in
Choosing from Existing User Agents LIst
Pasting your own User Agent String.