Make sure string constructors are efficient on literals

Make sure string constructors are efficient on literals

Separate out the overload when the length is not known, and be sure that
strlen() call is in the header so that strlen("foo") => 3 (since many
compilers support this optimization).

Also delete some unused types.

BUG=pdfium:151
R=thestig@chromium.org

Committed: https://pdfium.googlesource.com/pdfium/+/2cf0d21788974dd1ea19a68259c4fbccb0e56897

[Tom Sepez, 2015-05-05 20:26:26]

tsepez@chromium.org changed reviewers:
+ thestig@chromium.org

[Tom Sepez, 2015-05-05 20:26:27]

Lei, more string changes.

[Lei Zhang, 2015-05-05 21:31:56]

lgtm

https://codereview.chromium.org/1117263004/diff/1/core/include/fxcrt/fx_string.h
File core/include/fxcrt/fx_string.h (right):

https://codereview.chromium.org/1117263004/diff/1/core/include/fxcrt/fx_strin...
core/include/fxcrt/fx_string.h:207: CFX_ByteString(FX_LPCSTR ptr)
We should mark a whole bunch of these ctors explicit while we are here.

[Tom Sepez, 2015-05-05 22:11:16]

>
https://codereview.chromium.org/1117263004/diff/1/core/include/fxcrt/fx_strin...
> core/include/fxcrt/fx_string.h:207: CFX_ByteString(FX_LPCSTR ptr)
> We should mark a whole bunch of these ctors explicit while we are here.
Probably.  Though there's some precedent in std::string and WTF::String for
allowing promotion from literals,
so you can write fn("bar"); rather than fn(std::string("bar"));

[Tom Sepez, 2015-05-05 22:15:43]

Committed patchset #1 (id:1) manually as
2cf0d21788974dd1ea19a68259c4fbccb0e56897 (presubmit successful).