Add extra frame when dex_pc is non-zero.

Use the art dex file library to read the dex data.

Add unit tests for the UnwindDexFile code.

Bug: 72070049

Test: All unit tests continue to pass.
Test: Dumped the backtrace of the 137-cfi test while running in interpreter
Test: mode and verified that the stack trace is correct. Did this on host
Test: and for arm/arm64.

Change-Id: Ia6f343318c5dd6968a954015a7d59fdf101575b0
diff --git a/libbacktrace/UnwindDexFile.h b/libbacktrace/UnwindDexFile.h
new file mode 100644
index 0000000..dd70aba
--- /dev/null
+++ b/libbacktrace/UnwindDexFile.h
@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2018 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 _LIBBACKTRACE_UNWIND_DEX_FILE_H
+#define _LIBBACKTRACE_UNWIND_DEX_FILE_H
+
+#include <stdint.h>
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include <dex/dex_file-inl.h>
+
+namespace unwindstack {
+class Memory;
+struct MapInfo;
+}  // namespace unwindstack
+
+class UnwindDexFile {
+ public:
+  UnwindDexFile() = default;
+  virtual ~UnwindDexFile() = default;
+
+  void GetMethodInformation(uint64_t dex_offset, std::string* method_name, uint64_t* method_offset);
+
+  static UnwindDexFile* Create(uint64_t dex_file_offset_in_memory, unwindstack::Memory* memory,
+                               unwindstack::MapInfo* info);
+
+ protected:
+  std::unique_ptr<const art::DexFile> dex_file_;
+};
+
+class UnwindDexFileFromFile : public UnwindDexFile {
+ public:
+  UnwindDexFileFromFile() = default;
+  virtual ~UnwindDexFileFromFile();
+
+  bool Open(uint64_t dex_file_offset_in_file, const std::string& name);
+
+ private:
+  void* mapped_memory_ = nullptr;
+  size_t size_ = 0;
+};
+
+class UnwindDexFileFromMemory : public UnwindDexFile {
+ public:
+  UnwindDexFileFromMemory() = default;
+  virtual ~UnwindDexFileFromMemory() = default;
+
+  bool Open(uint64_t dex_file_offset_in_memory, unwindstack::Memory* memory);
+
+ private:
+  std::vector<uint8_t> memory_;
+};
+
+#endif  // _LIBBACKTRACE_UNWIND_DEX_FILE_H