Synthesize proper keyIdentifier for devtools protocol key events.
When bug 472077 moved devtools protocol key handling to browser one part
of code that sythesized keyIdentifier was lost (it was prevoiusly
handled in InspectorInputClient::dispatchKeyEvent and removed in
https://codereview.chromium.org/
1063653002/patch/40001/50004). Restore
that functionality else sending some key events (like enter) is not
handled correctly.
BUG=
Review URL: https://codereview.chromium.org/
1148803002
Cr-Commit-Position: refs/heads/master@{#331546}