More simplification and unification of frame handling

src/crankshaft/arm/lithium-arm.cc

Index: src/crankshaft/arm/lithium-arm.cc
diff --git a/src/crankshaft/arm/lithium-arm.cc b/src/crankshaft/arm/lithium-arm.cc
index d4e7ec936d373e7f9df69ce19a705c894012ba9c..6eb9337f5cb4627afc2dcadd7055e6f2adad2c94 100644
--- a/src/crankshaft/arm/lithium-arm.cc
+++ b/src/crankshaft/arm/lithium-arm.cc
@@ -383,8 +383,8 @@ void LTransitionElementsKind::PrintDataTo(StringStream* stream) {
 
 int LPlatformChunk::GetNextSpillIndex(RegisterKind kind) {
   // Skip a slot if for a double-width slot.
-  if (kind == DOUBLE_REGISTERS) spill_slot_count_++;
-  return spill_slot_count_++;
+  if (kind == DOUBLE_REGISTERS) current_frame_slots_++;
+  return current_frame_slots_++;
 }
 
 
@@ -2456,6 +2456,7 @@ LInstruction* LChunkBuilder::DoUnknownOSRValue(HUnknownOSRValue* instr) {
       Retry(kTooManySpillSlotsNeededForOSR);
       spill_index = 0;
     }
+    spill_index += StandardFrameConstants::kFixedSlotCount;
   }
   return DefineAsSpilled(new(zone()) LUnknownOSRValue, spill_index);
 }