Fix flaky 137-cfi test.

Avoid modifying the native debug info while we are unwinding.

Bug: 111411286
Test: test.py --host -b -r -t 137-cfi
Change-Id: Ie5a173d0fb545011413fa0326135aa9c56006e8d
diff --git a/runtime/jit/debugger_interface.h b/runtime/jit/debugger_interface.h
index 5bb4682..19507b0 100644
--- a/runtime/jit/debugger_interface.h
+++ b/runtime/jit/debugger_interface.h
@@ -27,6 +27,7 @@
 namespace art {
 
 class DexFile;
+class Mutex;
 class Thread;
 
 // This method is declared in the compiler library.
@@ -60,6 +61,11 @@
 // Returns approximate memory used by debug info for JIT code.
 size_t GetJitMiniDebugInfoMemUsage();
 
+// Get the lock which protects the native debug info.
+// Used only in tests to unwind while the JIT thread is running.
+// TODO: Unwinding should be race-free. Remove this.
+Mutex* GetNativeDebugInfoLock();
+
 }  // namespace art
 
 #endif  // ART_RUNTIME_JIT_DEBUGGER_INTERFACE_H_