Fix break position not to be outside of the script

Review URL: http://codereview.chromium.org/3017021

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5131 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/runtime.cc

@@ -9381,6 +9381,13 @@ static Object* Runtime_SetScriptBreakPoint(Arguments args) {
     }
     Debug::SetBreakPoint(shared, break_point_object_arg, &position);
     position += shared->start_position();
+
+    // The result position may become beyond script source end.
+    // This is expected when the function is toplevel. This may become
+    // a problem later when actual position gets converted into line/column.
+    if (shared->is_toplevel() && position == shared->end_position()) {
+      position = shared->end_position() - 1;
+    }
     return Smi::FromInt(position);
   }
   return  Heap::undefined_value();

test/mjsunit/debug-setbreakpoint.js

@@ -192,3 +192,26 @@ Debug.setListener(breakListener);
 sourceUrlFunc();
 
 assertTrue(breakListenerCalled, "Break listener not called on breakpoint set by sourceURL");
+
+
+// Breakpoint in a script with no statements test case. If breakpoint is set
+// to the script body, its actual position is taken from the nearest statement
+// below or like in this case is reset to the very end of the script.
+// Unless some precautions made, this position becomes out-of-range and
+// we get an exception.
+
+// Gets a script of 'i1' function and sets the breakpoint at line #4 which
+// should be empty.
+function SetBreakpointInI1Script() {
+  var i_script = Debug.findScript(i1);
+  assertTrue(!!i_script, "invalid script for i1");
+  Debug.setScriptBreakPoint(Debug.ScriptBreakPointType.ScriptId,
+                            i_script.id, 4);
+}
+
+// Creates the eval script and tries to set the breakpoint.
+// The tricky part is that the script function must be strongly reachable at the
+// moment. Since there's no way of simply getting the pointer to the function,
+// we run this code while the script function is being activated on stack.
+eval('SetBreakpointInI1Script()\nfunction i1(){}\n\n\n\nfunction i2(){}\n');
+