Implement CFI for JNI.

CFI is necessary for stack unwinding in gdb, lldb, and libunwind.

Change-Id: I37eb7973f99a6975034cf0e699e138c3a9aba10f
diff --git a/compiler/utils/assembler.cc b/compiler/utils/assembler.cc
index 5340dd3..36342c6 100644
--- a/compiler/utils/assembler.cc
+++ b/compiler/utils/assembler.cc
@@ -105,6 +105,9 @@
   CHECK_EQ(Size(), old_size);
 }
 
+void DebugFrameOpCodeWriterForAssembler::ImplicitlyAdvancePC() {
+  this->AdvancePC(assembler_->CodeSize());
+}
 
 Assembler* Assembler::Create(InstructionSet instruction_set) {
   switch (instruction_set) {