Allow dumping just CFI data from debug symbols

The inverse of what the existing code allows (skipping CFI), we'd like to be
able to skip everything *but* CFI. We're using this code for in-process
unwinding, and we don't need function or line info, so skipping it saves us
time. I've changed the 'bool cfi' parameter into an enum for more flexibility so
you can specify ALL_SYMBOL_DATA, NO_CFI or ONLY_CFI.

[Lei Zhang (chromium)]

Looks good overall. Basically all nits:

http://breakpad.appspot.com/517002/diff/1/src/common/linux/dump_symbols.cc
File src/common/linux/dump_symbols.cc (right):

http://breakpad.appspot.com/517002/diff/1/src/common/linux/dump_symbols.cc#ne...
src/common/linux/dump_symbols.cc:548: fprintf(stderr, "%s: \".stab\" section
found, but failed to load STABS"
80 col.

http://breakpad.appspot.com/517002/diff/1/src/common/linux/dump_symbols.cc#ne...
src/common/linux/dump_symbols.cc:569: if (symbol_data != NO_CFI) {
nit: not everything inside this new if block is indented correctly now.

http://breakpad.appspot.com/517002/diff/1/src/common/mac/dump_syms.h
File src/common/mac/dump_syms.h (right):

http://breakpad.appspot.com/517002/diff/1/src/common/mac/dump_syms.h#newcode56
src/common/mac/dump_syms.h:56: DumpSymbols(SymbolData symbol_data)
explicit DumpSymbols(...

http://breakpad.appspot.com/517002/diff/1/src/common/mac/dump_syms.h#newcode115
src/common/mac/dump_syms.h:115: // |stream|.Return true on success; if an error
occurs, report it and return false.
nit: space before Return. Wrap at 80 col.

http://breakpad.appspot.com/517002/diff/1/src/common/mac/dump_syms.h#newcode144
src/common/mac/dump_syms.h:144: SymbolData symbol_data_;
nit: const?

http://breakpad.appspot.com/517002/diff/1/src/common/mac/dump_syms.mm
File src/common/mac/dump_syms.mm (right):

http://breakpad.appspot.com/517002/diff/1/src/common/mac/dump_syms.mm#newcode376
src/common/mac/dump_syms.mm:376: : dumper_(dumper), module_(module),
reader_(reader), symbol_data_(symbol_data) { }
80 col.

http://breakpad.appspot.com/517002/diff/1/src/common/mac/dump_syms.mm#newcode385
src/common/mac/dump_syms.mm:385: SymbolData symbol_data_;
nit: const

http://breakpad.appspot.com/517002/diff/1/src/common/mac/dump_syms.mm#newcode409
src/common/mac/dump_syms.mm:409: mach_o::SectionMap::const_iterator debug_frame
You can do the if (symbol_data_ != NO_CFI) check first and skip looking up the
debug frame section.

http://breakpad.appspot.com/517002/diff/1/src/common/symbol_data.h
File src/common/symbol_data.h (right):

http://breakpad.appspot.com/517002/diff/1/src/common/symbol_data.h#newcode3
src/common/symbol_data.h:3: // Copyright (c) 2012 Google Inc.
It's 2013 now.

[Lei Zhang (chromium)]

lgtm