Reduce type-impedance for ExceptionMessages::failedTo* functions

These functions are always called with string literals, so having the
functions accept Strings means all callers have to perform implicit
conversions.
By modifying the signatures to use 'const char*' for these cases, these
conversion can be avoided (in the callers) and only be performed in the
functions themselves.
This reduces code size by ~70kB (Linux, x86-64, gcc-4.8.2).

Review URL: https://codereview.chromium.org/216633002

git-svn-id: svn://svn.chromium.org/blink/trunk@170304 bbb929c8-8fbe-4397-9dbb-9b2b20218538
2 files changed