Add the --steal-breakpoints flag.

runtime/vm/debugger.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/debugger.h"
 
 #include "include/dart_api.h"
 
 #include "vm/code_generator.h"
 #include "vm/code_patcher.h"
@@ skipping 17 matching lines @@
 #include "vm/visitor.h"
 
 
 namespace dart {
 
 DEFINE_FLAG(bool, show_invisible_frames, false,
             "Show invisible frames in debugger stack traces");
 DEFINE_FLAG(bool, trace_debugger_stacktrace, false,
             "Trace debugger stacktrace collection");
 DEFINE_FLAG(bool, verbose_debug, false, "Verbose debugger messages");
+DEFINE_FLAG(bool, steal_breakpoints, false,
+            "Intercept breakpoints and other pause events before they "

[rmacnak, 2015/04/30 21:48:55]

Should probably indicate they go to the vm service/observatory instead.

[turnidge, 2015/05/01 16:54:15]

Done.

+            "are sent to the embedder");
 
 
 Debugger::EventHandler* Debugger::event_handler_ = NULL;
 
 
 class RemoteObjectCache : public ZoneAllocated {
  public:
   explicit RemoteObjectCache(intptr_t initial_size);
   intptr_t AddObject(const Object& obj);
   RawObject* GetObj(intptr_t obj_id) const;
@@ skipping 184 matching lines @@
   // may go into a message loop and the Service will not.
   //
   // kBreakpointResolved events are handled differently in the vm
   // service, so suppress them here.
   if (Service::NeedsEvents() &&
       (event->type() != DebuggerEvent::kBreakpointResolved)) {
     ServiceEvent service_event(event);
     Service::HandleEvent(&service_event);
   }
 
-  if (event_handler_ != NULL) {
+  if (FLAG_steal_breakpoints && event->IsPauseEvent()) {
+    // We allow the embedder's default breakpoint handler to be overridden.
+    isolate_->PauseEventHandler();
+  } else if (event_handler_ != NULL) {
     (*event_handler_)(event);
   }
 
   if (Service::NeedsEvents() && event->IsPauseEvent()) {
     // If we were paused, notify the service that we have resumed.
     ServiceEvent service_event(event->isolate(), ServiceEvent::kResume);
     service_event.set_top_frame(event->top_frame());
     Service::HandleEvent(&service_event);
   }
 }
@@ skipping 2386 matching lines @@
 }
 
 
 void Debugger::RegisterCodeBreakpoint(CodeBreakpoint* bpt) {
   ASSERT(bpt->next() == NULL);
   bpt->set_next(code_breakpoints_);
   code_breakpoints_ = bpt;
 }
 
 }  // namespace dart