Reland: Debugger: deduplicate shared function info when setting script break points.

test/mjsunit/regress/regress-3960.js

+// Copyright 2015 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
+
+// Test that setting break point is works correctly when the debugger is
+// activated late, which leads to duplicate shared function infos.
+
+(function() {
+  var Debug = %GetDebugContext().Debug;
+
+  function listener(event, exec_state, event_data, data) {
+    if (event != Debug.DebugEvent.Break) return;
+    try {
+      assertTrue(/foo/.test(exec_state.frame(0).sourceLineText()));
+      break_count++;
+    } catch (e) {
+      exception = e;
+    }
+  }
+
+  for (var i = 0; i < 3; i++) {
+    var foo = function() { a = 1; }
+    var exception = null;
+    var break_count = 0;
+    Debug.setListener(listener);
+    if (i < 2) Debug.setBreakPoint(foo, 0, 0);
+    assertTrue(/\[B\d\]a = 1/.test(Debug.showBreakPoints(foo)));
+    foo();
+    assertEquals(1, break_count);
+    assertNull(exception);
+  }
+
+  Debug.setListener(null);
+})();