Compact the symbol table when creating core snapshots or JIT app snapshots.

runtime/vm/dart_api_impl.cc

Index: runtime/vm/dart_api_impl.cc
diff --git a/runtime/vm/dart_api_impl.cc b/runtime/vm/dart_api_impl.cc
index 22e23911615cecd9d72dcd545b018d2983ff3b1b..547a23d0e41ed19cf4f5eae26724da4e86f6db69 100644
--- a/runtime/vm/dart_api_impl.cc
+++ b/runtime/vm/dart_api_impl.cc
@@ -1577,6 +1577,8 @@ Dart_CreateSnapshot(uint8_t** vm_isolate_snapshot_buffer,
   I->heap()->IterateObjects(&check_canonical);
 #endif  // #if defined(DEBUG)
 
+  Symbols::Compact(I);
+
   FullSnapshotWriter writer(Snapshot::kCore, vm_isolate_snapshot_buffer,
                             isolate_snapshot_buffer, ApiReallocate,
                             NULL /* instructions_writer */);
@@ -6765,6 +6767,8 @@ Dart_CreateAppJITSnapshotAsBlobs(uint8_t** isolate_snapshot_buffer,
   }
   I->StopBackgroundCompiler();
 
+  Symbols::Compact(I);
+
   NOT_IN_PRODUCT(TimelineDurationScope tds2(T, Timeline::GetIsolateStream(),
                                             "WriteAppJITSnapshot"));
   BlobInstructionsWriter instructions_writer(instructions_blob_buffer,