Implement core dump to minidump conversion.

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. Turn the LinuxDumper class into a base class and move ptrace related
   code into a new derived class, LinuxPtraceDumper.
2. Add a LinuxCoreDumper class, which is derived from LinuxDumper, to
   extract information from a crashed process via a core dump file instead
   of ptrace.
3. Add a WriteMinidumpFromCore function to
     src/client/linux/minidump_writer/minidump_writer.h,
   which uses LinuxCoreDumper to extract information from a core dump file.
4. Add a core2md utility, which simply wraps WriteMinidumpFromCore, for
   converting a core dump to a minidump.

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.
4. Run Chromium OS tests to test core2md.
Review URL: http://breakpad.appspot.com/343001

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@905 4c0a9323-5329-0410-9bdc-e9ce6186880e

src/common/linux/elf_core_dump_unittest.cc

@@ -141,7 +141,7 @@ TEST(ElfCoreDumpTest, ValidCoreFile) {
   // TODO(benchan): Revert to use ASSERT_TRUE once the flakiness in
   // CrashGenerator is identified and fixed.
   if (!crash_generator.CreateChildCrash(kNumOfThreads, kCrashThread,
-                                        kCrashSignal)) {
+                                        kCrashSignal, NULL)) {
     fprintf(stderr, "ElfCoreDumpTest.ValidCoreFile test is skipped "
             "due to no core dump generated");
     return;

src/common/linux/tests/crash_generator.cc

@@ -144,7 +144,8 @@ bool CrashGenerator::SetCoreFileSizeLimit(rlim_t limit) const {
 }
 
 bool CrashGenerator::CreateChildCrash(
-    unsigned num_threads, unsigned crash_thread, int crash_signal) {
+    unsigned num_threads, unsigned crash_thread, int crash_signal,
+    pid_t* child_pid) {
   if (num_threads == 0 || crash_thread >= num_threads)
     return false;
 
@@ -178,6 +179,9 @@ bool CrashGenerator::CreateChildCrash(
     perror("CrashGenerator: Child process not killed by the expected signal");
     return false;
   }
+
+  if (child_pid)
+    *child_pid = pid;
   return true;
 }
 

src/common/linux/tests/crash_generator.h

@@ -70,7 +70,7 @@ class CrashGenerator {
   // a signal with number |crash_signal| to the |crash_thread|-th thread.
   // Returns true on success.
   bool CreateChildCrash(unsigned num_threads, unsigned crash_thread,
-                        int crash_signal);
+                        int crash_signal, pid_t* child_pid);
 
   // Creates |num_threads| threads in the child process.
   void CreateThreadsInChildProcess(unsigned num_threads);