[snapshot] Refactored snapshot functions to no longer copy.

Bug: v8:8015
Change-Id: Id459da19e009b2203b12ba04d185dc857e4913c1
Reviewed-on: https://chromium-review.googlesource.com/1209786Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Florian Sattler <sattlerf@google.com>
Cr-Commit-Position: refs/heads/master@{#55700}

src/snapshot/builtin-snapshot-utils.cc

@@ -50,7 +50,7 @@ BuiltinSnapshotUtils::BytecodeFromIndex(int index) {
 
 // static
 void BuiltinSnapshotUtils::ForEachBytecode(
-    std::function<void(Bytecode, OperandScale)> f) {
+    const std::function<void(Bytecode, OperandScale)>& f) {
   static const OperandScale kOperandScales[] = {
 #define VALUE(Name, _) OperandScale::k##Name,
       OPERAND_SCALE_LIST(VALUE)

src/snapshot/builtin-snapshot-utils.h

@@ -52,7 +52,8 @@ class BuiltinSnapshotUtils : public AllStatic {
 
   // Iteration over all {bytecode,operand_scale} pairs. Implemented here since
   // (de)serialization depends on the iteration order.
-  static void ForEachBytecode(std::function<void(Bytecode, OperandScale)> f);
+  static void ForEachBytecode(
+      const std::function<void(Bytecode, OperandScale)>& f);
 #endif  // V8_EMBEDDED_BYTECODE_HANDLERS
 };
 

src/snapshot/default-deserializer-allocator.cc

@@ -121,7 +121,7 @@ HeapObject* DefaultDeserializerAllocator::GetObject(AllocationSpace space,
 }
 
 void DefaultDeserializerAllocator::DecodeReservation(
-    std::vector<SerializedData::Reservation> res) {
+    const std::vector<SerializedData::Reservation>& res) {
   DCHECK_EQ(0, reservations_[FIRST_SPACE].size());
   int current_space = FIRST_SPACE;
   for (auto& r : res) {

src/snapshot/default-deserializer-allocator.h

@@ -58,7 +58,7 @@ class DefaultDeserializerAllocator final {
   // ------- Reservation Methods -------
   // Methods related to memory reservations (prior to deserialization).
 
-  void DecodeReservation(std::vector<SerializedData::Reservation> res);
+  void DecodeReservation(const std::vector<SerializedData::Reservation>& res);
   bool ReserveSpace();
 
   // Atomically reserves space for the two given deserializers. Guarantees