posix: clean up shared memory code

posix: clean up shared memory code

At first I rewrote this to use the shm_*() family of
functions, but that doesn't work on OS X.  Now I've just
cleaned up some bits and added an extra print to help with
the below bug.

BUG=16371

[agl, 2009-09-15 19:26:05]

http://codereview.chromium.org/204024/diff/1/3
File base/shared_memory_posix.cc (right):

http://codereview.chromium.org/204024/diff/1/3#newcode145
Line 145: if (file == EEXIST)
Wouldn't file == -1 and errno == EEXIST?

http://codereview.chromium.org/204024/diff/1/3#newcode167
Line 167: return false;
leaking |file|

http://codereview.chromium.org/204024/diff/1/3#newcode171
Line 171: return false;
leaking |file|

http://codereview.chromium.org/204024/diff/1/3#newcode173
Line 173: return false;
leaking |file|

http://codereview.chromium.org/204024/diff/1/3#newcode177
Line 177: mapped_file_ = dup(file);
Why dup? Previously it was because FILE can't be told to release its descriptor.

http://codereview.chromium.org/204024/diff/1/3#newcode181
Line 181: return false;
leaking |file|

[Evan Martin, 2009-09-15 19:31:27]

new upload; clicking "delta from patch set 1" will show all the changes from the
version you reviewed

[agl, 2009-09-15 19:34:13]

LPGTM

http://codereview.chromium.org/204024/diff/5001/8
File base/shared_memory_posix.cc (right):

http://codereview.chromium.org/204024/diff/5001/8#newcode152
Line 152: shm_unlink(mem_name.c_str());
If (file < 0), you're unlinking someone else's shared memory.

[Evan Martin, 2009-09-16 17:32:02]

this is the patch you looked at last night

[agl, 2009-09-16 17:34:09]

LGTM