Add debugger protocol request for setting global flags.

test/mjsunit/debug-enable-disable-breakpoints.js

 // Copyright 2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 70 matching lines @@
 // Enable both breakpoints.
 Debug.enableBreakPoint(bp1);
 Debug.enableBreakPoint(bp2);
 f();
 assertEquals(5, break_point_hit_count);
 
 // Disable the first breakpoint.
 Debug.disableBreakPoint(bp1);
 f();
 assertEquals(6, break_point_hit_count);
+
+// Deactivate all breakpoints.
+Debug.debuggerFlags().breakPointsActive.setValue(false);
+f();
+assertEquals(6, break_point_hit_count);
+
+// Enable the first breakpoint.
+Debug.enableBreakPoint(bp1);
+f();
+assertEquals(6, break_point_hit_count);
+
+// Activate all breakpoints.
+Debug.debuggerFlags().breakPointsActive.setValue(true);
+f();
+assertEquals(7, break_point_hit_count);