Update the Unwinder object and add tests.

Changes:
- Remove unused GetReturnAddressFromDefault function and tests.
- Modify the unwinder to stop when a pc/sp in a device map.
- Modify the unwinder to skip initial frames based on map names.
- Unit tests that exercise all of the paths in the unwinder code.
- Move the test Elf/ElfInterface objects into their own file.
- Update RegsFake to handle extra cases.
- Modify libbacktrace code to use this unwinder.

The new unwinder does not implement the ignore frame functionality since
this is not used very often and is better implemented using a skip frames
in named libraries functionality.

Test: Ran new unit tests, ran backtrace tests.
Change-Id: Ifd65e9acd66ac5e2d0e04bd32a9ad870b54610ff
diff --git a/libunwindstack/tests/ElfFake.h b/libunwindstack/tests/ElfFake.h
new file mode 100644
index 0000000..4359bca
--- /dev/null
+++ b/libunwindstack/tests/ElfFake.h
@@ -0,0 +1,84 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _LIBUNWINDSTACK_TESTS_ELF_FAKE_H
+#define _LIBUNWINDSTACK_TESTS_ELF_FAKE_H
+
+#include <stdint.h>
+
+#include <deque>
+#include <string>
+
+#include <unwindstack/Elf.h>
+#include <unwindstack/ElfInterface.h>
+#include <unwindstack/Memory.h>
+#include <unwindstack/Regs.h>
+
+namespace unwindstack {
+
+struct StepData {
+  StepData(uint64_t pc, uint64_t sp, bool finished) : pc(pc), sp(sp), finished(finished) {}
+  uint64_t pc;
+  uint64_t sp;
+  bool finished;
+};
+
+struct FunctionData {
+  FunctionData(std::string name, uint64_t offset) : name(name), offset(offset) {}
+
+  std::string name;
+  uint64_t offset;
+};
+
+class ElfFake : public Elf {
+ public:
+  ElfFake(Memory* memory) : Elf(memory) { valid_ = true; }
+  virtual ~ElfFake() = default;
+
+  void FakeSetInterface(ElfInterface* interface) { interface_.reset(interface); }
+};
+
+class ElfInterfaceFake : public ElfInterface {
+ public:
+  ElfInterfaceFake(Memory* memory) : ElfInterface(memory) {}
+  virtual ~ElfInterfaceFake() = default;
+
+  bool Init() override { return false; }
+  void InitHeaders() override {}
+  bool GetSoname(std::string*) override { return false; }
+
+  bool GetFunctionName(uint64_t, std::string*, uint64_t*) override;
+
+  bool Step(uint64_t, Regs*, Memory*, bool*) override;
+
+  void FakeSetLoadBias(uint64_t load_bias) { load_bias_ = load_bias; }
+
+  static void FakePushFunctionData(const FunctionData data) { functions_.push_back(data); }
+  static void FakePushStepData(const StepData data) { steps_.push_back(data); }
+
+  static void FakeClear() {
+    functions_.clear();
+    steps_.clear();
+  }
+
+ private:
+  static std::deque<FunctionData> functions_;
+  static std::deque<StepData> steps_;
+};
+
+}  // namespace unwindstack
+
+#endif  // _LIBUNWINDSTACK_TESTS_ELF_FAKE_H