Refactor LinuxDumper and MinidumpWriter.

Refactor LinuxDumper and MinidumpWriter.

This patch is part of a bigger patch that helps merging the breakpad code
with the modified version in Chromium OS.

Specifically, this patch makes the following changes:
1. Add two convenient methods, back() and empty(), to the wasteful_vector
   class.
2. Refactor the LinuxDumper class such that it can later be splitted into
   a base class and two derived classes, one uses the current ptrace
   implementation and one uses a core file.
3. Refactor the MinidumpWriter class such that it can later use different
   derived implementations of LinuxDumper.

BUG=455
TEST=Tested the following:
1. Build on 32-bit and 64-bit Linux with gcc 4.4.3 and gcc 4.6.
2. Build on Mac OS X 10.6.8 with gcc 4.2 and clang 3.0 (with latest gmock).
3. All unit tests pass.

[Ben Chan]

Instead making changes to LinuxDumper and splitting it into two derived classes
in one big patch, I think it may be easier to review as two patches. So some of
the changes in this patch may seem unnecessary/unintuitive, they are needed for
the next patch.

[Ben Chan]

http://breakpad.appspot.com/340001/diff/1/3
File src/client/linux/minidump_writer/linux_dumper.h (right):

http://breakpad.appspot.com/340001/diff/1/3#newcode69
Line 69: #elif defined(__x86_64)
Note: Just to make it consistent with the rest of the code.

http://breakpad.appspot.com/340001/diff/1/3#newcode132
Line 132: virtual bool GetThreadInfoByIndex(size_t index, ThreadInfo* info);
Note: In case with core files, it's more practical to get the thread info by
index. Since we always get from a thread info from |threads_|, I change this
method to take an index.

http://breakpad.appspot.com/340001/diff/1/3#newcode171
Line 171: uintptr_t crash_address() const { return crash_address_; }
Note: In case of core files, we won't know the information about crash address,
signal, and thread ID until after processing the core file. So I make
LinuxDumper (and later its derived classes) return these information to
MinidumpWriter.

[Lei Zhang (chromium)]

LGTM with nits below

http://breakpad.appspot.com/340001/diff/1/3
File src/client/linux/minidump_writer/linux_dumper.h (right):

http://breakpad.appspot.com/340001/diff/1/3#newcode149
Line 149: void CopyFromProcess(void* dest, pid_t child, const void* src,
This can stay static since it doesn't access any member variables.

http://breakpad.appspot.com/340001/diff/1/5
File src/client/linux/minidump_writer/minidump_writer.cc (right):

http://breakpad.appspot.com/340001/diff/1/5#newcode1284
Line 1284: void* Alloc(unsigned bytes) {
nit: put this with GetCrashThread() ?

[Ben Chan]

http://breakpad.appspot.com/340001/diff/1/3
File src/client/linux/minidump_writer/linux_dumper.h (right):

http://breakpad.appspot.com/340001/diff/1/3#newcode149
Line 149: void CopyFromProcess(void* dest, pid_t child, const void* src,
On 2012/01/11 01:23:41, thestig wrote:
> This can stay static since it doesn't access any member variables.

In case of core files, the derived implementation needs to access member
variables, so I made it a member method.

http://breakpad.appspot.com/340001/diff/1/5
File src/client/linux/minidump_writer/minidump_writer.cc (right):

http://breakpad.appspot.com/340001/diff/1/5#newcode1284
Line 1284: void* Alloc(unsigned bytes) {
On 2012/01/11 01:23:41, thestig wrote:
> nit: put this with GetCrashThread() ?

Done.