This issue is easy to reproduce and is present in both WebStorm 2017.2 and PhpStorm 2017.2.1 for Mac.
Open Preferences. Go to Editor -> Font. Just by staying on that page, the CPU usage will increase significantly and stays at an abnormally high level forever if you stay on that page, even if you don't do anything else. Worse, if I then go to for example Color Scheme->Color Scheme Font and then back to Editor-> Font, doing that enough times and an out-of-memory pop-up window will appear suggesting you to adjust the memory param for Java. Dismissing the pop-up without change anything will simply render the whole IDE unresponsive and the pop-up will appear again. I just click on Shutdown to terminate the IDE.
I wonder if anyone else can reproduce this.
I'm on MacOS 10.11.6.