Init .gnu_debugdata in GetElf().

- Modify the tests to share some code for the generation of the elf data.
- Move the gnu_debugdata files into a separate directory.
- Add tests for GetElf().
- Move the CreateMemory() tests and the GetElf() tests into separate files.

Bug: 23762183

Test: New unit tests pass.
Change-Id: Ie3380296bb49753c2ac8801cfa11f93d6ff7121d
diff --git a/libunwindstack/MapInfo.cpp b/libunwindstack/MapInfo.cpp
index 051f700..d7b483d 100644
--- a/libunwindstack/MapInfo.cpp
+++ b/libunwindstack/MapInfo.cpp
@@ -73,13 +73,15 @@
   return new MemoryRange(memory, start, end);
 }
 
-Elf* MapInfo::GetElf(pid_t pid, bool) {
+Elf* MapInfo::GetElf(pid_t pid, bool init_gnu_debugdata) {
   if (elf) {
     return elf;
   }
 
   elf = new Elf(CreateMemory(pid));
-  elf->Init();
+  if (elf->Init() && init_gnu_debugdata) {
+    elf->InitGnuDebugdata();
+  }
   // If the init fails, keep the elf around as an invalid object so we
   // don't try to reinit the object.
   return elf;