More simplification and unification of frame handling

src/crankshaft/arm64/lithium-arm64.cc

Index: src/crankshaft/arm64/lithium-arm64.cc
diff --git a/src/crankshaft/arm64/lithium-arm64.cc b/src/crankshaft/arm64/lithium-arm64.cc
index 298e6b519f1256461c40fdb08758a71b9f932dd4..c4b0520cb1278ae3da40eab485230016982bbc8c 100644
--- a/src/crankshaft/arm64/lithium-arm64.cc
+++ b/src/crankshaft/arm64/lithium-arm64.cc
@@ -527,11 +527,7 @@ LUnallocated* LChunkBuilder::TempDoubleRegister() {
   return operand;
 }
 
-
-int LPlatformChunk::GetNextSpillIndex() {
-  return spill_slot_count_++;
-}
-
+int LPlatformChunk::GetNextSpillIndex() { return current_frame_slots_++; }
 
 LOperand* LPlatformChunk::GetNextSpillSlot(RegisterKind kind) {
   int index = GetNextSpillIndex();
@@ -2647,6 +2643,7 @@ LInstruction* LChunkBuilder::DoUnknownOSRValue(HUnknownOSRValue* instr) {
       Retry(kTooManySpillSlotsNeededForOSR);
       spill_index = 0;
     }
+    spill_index += StandardFrameConstants::kFixedSlotCount;
   }
   return DefineAsSpilled(new(zone()) LUnknownOSRValue, spill_index);
 }