Changed Google Icon - is this a virus or malware?

I was online at the Project Gutenberg Australia site - I downloaded several books. When I exited, a window popped up on my computer, saying it was installing or updating some program that I did not recognize - it concerned, and I tried to turn off my computer before it finished installing - but it was going very fast and I don't think I succeeded - I had unplugged the computer and removed the battery to try to disconnect quickly. When I turned it back on and got on the internet - the google favicon is different - looks kind of like a hamburger? A semi-circle on top - two lines in middle - then a semicircle on bottom - blue background - white icon. All other sites I go to have the correct icons.

I'm afraid to use my computer now in case this indicates spyware or malware. My Norton protection expired, and I haven't renewed? Do I have a problem?

Please download Malwarebytes Anti-Malware from here.

Double Click mbam-setup.exe to install the application.

• Make sure a checkmark is placed next to Update Malwarebytes' Anti-Malware and Launch Malwarebytes Anti-Malware, then click Finish.
  
• If an update is found, it will download and install the latest version.
  
• Once the program has loaded, select "Perform Full Scan", then click Scan.
  
• The scan may take some time to finish,so please be patient.
  
• When the scan is complete, click OK, then Show Results to view the results.
  
• Make sure that everything is checked, and click Remove Selected.
  
• When disinfection is completed, a log will open in Notepad and you may be prompted to Restart. (See Extra Note)
  
• Please save the log to a location you will remember.
  
• The log is automatically saved by MBAM and can be viewed by clicking the Logs tab in MBAM.
  
• Copy and paste the entire report in your next reply.
  

Extra Note:

If MBAM encounters a file that is difficult to remove,you will be presented with 1 of 2 prompts,click OK to either and let MBAM proceed with the disinfection process. If asked to restart the computer, please do so immediately.