Rename HNativeDebugInfo to HNop

We can generalize HNativeDebugInfo to be used as a Nop (i.e. no
instructions are generated), and give it the option of having an
environment to keep the current HNativeDebugInfo logic working.

Test: art/test/testrunner/testrunner.py --host --64 --optimizing -b
Change-Id: I06b3a36e8b124bcda858d2c9cd8ff0ab21caea36
diff --git a/compiler/optimizing/code_generator_arm64.cc b/compiler/optimizing/code_generator_arm64.cc
index 2f8c0b2..d3031b7 100644
--- a/compiler/optimizing/code_generator_arm64.cc
+++ b/compiler/optimizing/code_generator_arm64.cc
@@ -3852,12 +3852,12 @@
   }
 }
 
-void LocationsBuilderARM64::VisitNativeDebugInfo(HNativeDebugInfo* info) {
-  new (GetGraph()->GetAllocator()) LocationSummary(info);
+void LocationsBuilderARM64::VisitNop(HNop* nop) {
+  new (GetGraph()->GetAllocator()) LocationSummary(nop);
 }
 
-void InstructionCodeGeneratorARM64::VisitNativeDebugInfo(HNativeDebugInfo*) {
-  // MaybeRecordNativeDebugInfo is already called implicitly in CodeGenerator::Compile.
+void InstructionCodeGeneratorARM64::VisitNop(HNop*) {
+  // The environment recording already happened in CodeGenerator::Compile.
 }
 
 void CodeGeneratorARM64::IncreaseFrame(size_t adjustment) {