[debugger] omit exception events for rethrown exceptions in async.

test/mjsunit/harmony/async-debug-caught-exception.js

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax --harmony-async-await --expose-debug-as debug
+
+Debug = debug.Debug
+
+var exception = null;
+var log;
+
+function listener(event, exec_state, event_data, data) {
+  if (event != Debug.DebugEvent.Exception) return;
+  try {
+    var line = exec_state.frame(0).sourceLineText();
+    var match = /Exception (\w)/.exec(line);
+    assertNotNull(match);
+    log.push(match[1]);
+  } catch (e) {
+    exception = e;
+  }
+}
+
+async function thrower() {
+  throw "a";  // Exception a
+}
+
+async function caught_throw() {
+  try {
+    await thrower();
+  } catch (e) {
+    assertEquals("a", e);
+  }
+}
+
+
+// Caught throw, events on any exception.
+log = [];
+Debug.setListener(listener);
+Debug.setBreakOnException();
+caught_throw();
+%RunMicrotasks();
+Debug.setListener(null);
+Debug.clearBreakOnException();
+assertEquals(["a"], log);
+assertNull(exception);
+
+// Caught throw, events on uncaught exception.
+log = [];
+Debug.setListener(listener);
+Debug.setBreakOnUncaughtException();
+caught_throw();
+%RunMicrotasks();
+Debug.setListener(null);
+Debug.clearBreakOnUncaughtException();
+assertEquals([], log);
+assertNull(exception);
+
+var reject = Promise.reject("b");
+
+async function caught_reject() {
+  try {
+    await reject;
+  } catch (e) {
+    assertEquals("b", e);
+  }
+}
+
+// Caught reject, events on any exception.
+log = [];
+Debug.setListener(listener);
+Debug.setBreakOnException();
+caught_reject();
+%RunMicrotasks();
+Debug.setListener(null);
+Debug.clearBreakOnException();
+assertEquals([], log);
+assertNull(exception);
+
+// Caught reject, events on uncaught exception.
+log = [];
+Debug.setListener(listener);
+Debug.setBreakOnUncaughtException();
+caught_reject();
+%RunMicrotasks();
+Debug.setListener(null);
+Debug.clearBreakOnUncaughtException();
+assertEquals([], log);
+assertNull(exception);