[wasm] Add --trace-wasm-ast-start and --trace-wasm-ast-end options and improve tracing.

src/compiler/wasm-compiler.cc

Index: src/compiler/wasm-compiler.cc
diff --git a/src/compiler/wasm-compiler.cc b/src/compiler/wasm-compiler.cc
index 948598697cf47c38bad865f208579ac298f1b5a1..65568ce2626a163f20dd6167d0e8d2c4e3540ba0 100644
--- a/src/compiler/wasm-compiler.cc
+++ b/src/compiler/wasm-compiler.cc
@@ -2595,6 +2595,11 @@ Handle<Code> CompileWasmFunction(wasm::ErrorThrower& thrower, Isolate* isolate,
     return Handle<Code>::null();
   }
 
+  if (function.func_index >= FLAG_trace_wasm_ast_start &&
+      function.func_index < FLAG_trace_wasm_ast_end) {
+    PrintAst(body);
+  }
+
   if (FLAG_trace_wasm_decode_time) {
     decode_ms = decode_timer.Elapsed().InMillisecondsF();
   }