For the last couple of weeks, I couldn't write multi-line messages in Facebook on Google Chrome on Mac OS X. Some other web sites also had this problem. If I persisted in trying too much, then the browser tab would crash.
I solved this by deleting my Google Chrome Profile. I did it as follows:
1) I closed Google Chrome
2) I opened Terminal, by typing Terminal into Spotlight, and opening the "Top Hit".
3) In Terminal I typed the following (use copy + paste):
rm -rf ~/Library/Application\ Support/Google/Chrome/
4) I pressed the enter key
It took several seconds to complete. Once it finished, I opened Google Chrome, and it acted like it was opened for the first time. Facebook now lets me enter multi-line messages without crashing.