Fixes bug in file_util::ReplaceExtension that could chop off path...

Fixes bug in file_util::ReplaceExtension that could chop off path
elements. This was causing some folks bookmarks not to get saved!

BUG=1946
TEST=covered by unit tests


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=2412

[Erik does not do reviews, 2008-09-19 16:53:14]

http://codereview.chromium.org/2990/diff/1/2
File base/file_util.cc (right):

http://codereview.chromium.org/2990/diff/1/2#newcode198
Line 198: std::wstring::size_type last_dot = file_name->rfind(L'.');
Shouldn't we early out if last_dot == npos?

http://codereview.chromium.org/2990/diff/1/2#newcode204
Line 204: last_dot = file_name->size();
Again, shouldn't we just early out here?  The net result of this is that the
string is unchanged, but we do extra work that we didn't need to.

http://codereview.chromium.org/2990/diff/1/3
File base/file_util_unittest.cc (right):

http://codereview.chromium.org/2990/diff/1/3#newcode826
Line 826: ps.push_back(file_util::kPathSeparator);
you don't need this.  see next comment.

http://codereview.chromium.org/2990/diff/1/3#newcode829
Line 829: std::wstring file = ps + L"foo.bar" + ps + L"foo";
use AppendToPath

http://codereview.chromium.org/2990/diff/1/3#newcode831
Line 831: EXPECT_EQ(ps + L"foo.bar" + ps + L"foo.baz", file);
rather than build the path again, can you just make a copy of the original
before calling ReplaceExtension?  This will be less error prone.

[Erik does not do reviews, 2008-09-19 17:27:36]

LGTM

good find!