Revert 255397 "Fill out the rest of the StringPiece functions fo..."

> Fill out the rest of the StringPiece functions for 16-bit.
> 
> I was originally opposed to these since we didn't need them and they were complicated. But I'm wanting to use some of these functions in a different patch, so it seems like a good time to fill out the std::string-like finding functions for StringPiece16.
> 
> This deletes the old StringPieceDetails for which the only point was to share the common stuff between the two BasicStringPiece specializations.
> 
> I used the pattern of having two versions of each function declared in the header and then expanding the template in the .cc file, to avoid template bloat in the header.
> 
> This replaces all of the size_type goop with size_t. Chrome code assumes these are the same and we encourage people to just use size_t in loops, for example, rather than using the size_type of the template they're iterating over. This makes the code more readable in many places. It also solves a problem with declaration ordering since most of the functions that used size_type are now moved above where the size_type is actually declared.
> 
> R=viettrungluu@chromium.org
> TBR=akalin, ben
> 
> Review URL: https://codereview.chromium.org/187793004

TBR=brettw@chromium.org

Review URL: https://codereview.chromium.org/189793002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255492 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255492
Fix clang compilation for oobe_localization_browsertest.cc

BUG=none
TEST=N/A

Review URL: https://codereview.chromium.org/189233003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255493 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255493