Fix precompiler

runtime/vm/precompiler.cc

Index: runtime/vm/precompiler.cc
diff --git a/runtime/vm/precompiler.cc b/runtime/vm/precompiler.cc
index 3743b1efe72e1f0904c7a17b47596758c05ab328..e61e916218cb9abe1876e1b26fdccf377f39076b 100644
--- a/runtime/vm/precompiler.cc
+++ b/runtime/vm/precompiler.cc
@@ -2013,7 +2013,12 @@ bool PrecompileParsedFunctionHelper::Compile(CompilationPipeline* pipeline) {
                                   "OptimizationPasses");
 #endif  // !PRODUCT
         inline_id_to_function.Add(&function);
-        inline_id_to_token_pos.Add(function.token_pos());
+        // We do not add the token position now because we don't know the
+        // position of the inlined call until later. A side effect of this
+        // is that the length of |inline_id_to_function| is always larger
+        // than the length of |inline_id_to_token_pos| by one.
+        // Top scope function has no caller (-1). We do this because we expect
+        // all token positions to be at an inlined call.
         // Top scope function has no caller (-1).
         caller_inline_id.Add(-1);
         CSTAT_TIMER_SCOPE(thread(), graphoptimizer_timer);