Hardware acceleration for flash videos in Google Chrome
Step 1 would be to look the status of your Chrome GPU settings.

Paste this "chrome://gpu/" in Chrome web address field.

On my MBA 10.9.5 Chrome Version 38.0.2125.101 it looks like this

Graphics Feature Status
Canvas: Hardware accelerated
Flash: Hardware accelerated
Flash Stage3D: Hardware accelerated
Flash Stage3D Baseline profile: Hardware accelerated
Compositing: Hardware accelerated
Rasterization: Software only, hardware acceleration unavailable
Threaded Rasterization: Disabled
Video Decode: Software only, hardware acceleration unavailable
Video Encode: Hardware accelerated
WebGL: Hardware accelerated



Pending on your result (Flash- Not accelerated) proceed to step 2:


Do following: 


  To force Chrome / Chromium to use hardware acceleration, open a new
  tab, type "chrome://flags" (without quotes), search for "Override
  software rendering list", enable it and restart Chrome / Chromium.



Optional Step 3 (my settings)


Paste this "chrome://plugins/" in web address field.

Disable the Chrome build in Adobe Flash player aka PepperFlashPlayer.plugin

If you have not already have done so, get the Adobe Flash player from Adobe, that will be now used by Chrome.