Fix compilation warnings/errors seen with newer versions of gcc compiler.

runtime/vm/snapshot.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/snapshot.h"
 
 #include "vm/assert.h"
 #include "vm/bootstrap.h"
 #include "vm/heap.h"
 #include "vm/object.h"
@@ skipping 21 matching lines @@
 
 static bool IsObjectStoreTypeId(intptr_t index) {
   // Check if this is a type which is stored in the object store.
   return (index >= ObjectStore::kObjectType &&
           index <= ObjectStore::kBoolInterface);
 }
 
 
 // TODO(5411462): Temporary setup of snapshot for testing purposes,
 // the actual creation of a snapshot maybe done differently.
-Snapshot* Snapshot::SetupFromBuffer(void* raw_memory) {
+const Snapshot* Snapshot::SetupFromBuffer(const void* raw_memory) {
   ASSERT(raw_memory != NULL);
   ASSERT(kHeaderSize == sizeof(Snapshot));
   ASSERT(kLengthIndex == length_offset());
   ASSERT((kSnapshotFlagIndex * sizeof(int32_t)) == full_snapshot_offset());
   ASSERT((kHeapObjectTag & kInlined));
   ASSERT((kHeapObjectTag & kObjectId));
   ASSERT((kObjectAlignmentMask & kObjectId) == kObjectId);
-  Snapshot* snapshot = reinterpret_cast<Snapshot*>(raw_memory);
+  const Snapshot* snapshot = reinterpret_cast<const Snapshot*>(raw_memory);
   return snapshot;
 }
 
 
 RawObject* SnapshotReader::ReadObject() {
   intptr_t header = Read<intptr_t>();
   if ((header & kSmiTagMask) == 0) {
     return reinterpret_cast<RawObject*>(header);
   }
   return ReadObjectImpl(header);
@@ skipping 366 matching lines @@
 
 
 void SnapshotWriterVisitor::VisitPointers(RawObject** first, RawObject** last) {
   for (RawObject** current = first; current <= last; current++) {
     RawObject* raw_obj = *current;
     writer_->WriteObject(raw_obj);
   }
 }
 
 }  // namespace dart