Delete deprecated header file.

It was moved to platform/WebArrayBuffer.h and all references are now gone.

BUG=245025
R=abarth@chromium.org

Review URL: https://codereview.chromium.org/19490003

git-svn-id: svn://svn.chromium.org/blink/trunk@154442 bbb929c8-8fbe-4397-9dbb-9b2b20218538