Add breakpoints and single-stepping to Observatory.

runtime/vm/json_stream.h

Index: runtime/vm/json_stream.h
diff --git a/runtime/vm/json_stream.h b/runtime/vm/json_stream.h
index 08371e185781b522d4d9b4bc5afeb2dbf293fb2e..3fc4961e61ae470802d037ae956f9ea35a992906 100644
--- a/runtime/vm/json_stream.h
+++ b/runtime/vm/json_stream.h
@@ -101,6 +101,7 @@ class JSONStream : ValueObject {
   void PrintProperty(const char* name, const Object& o, bool ref = true);
 
   void PrintProperty(const char* name, const DebuggerEvent* event);
+  void PrintProperty(const char* name, SourceBreakpoint* bpt);
   void PrintProperty(const char* name, Isolate* isolate);
   void PrintPropertyName(const char* name);
   void PrintCommaIfNeeded();
@@ -164,6 +165,9 @@ class JSONObject : public ValueObject {
   void AddProperty(const char* name, const DebuggerEvent* event) const {
     stream_->PrintProperty(name, event);
   }
+  void AddProperty(const char* name, SourceBreakpoint* bpt) const {
+    stream_->PrintProperty(name, bpt);
+  }
   void AddProperty(const char* name, Isolate* isolate) const {
     stream_->PrintProperty(name, isolate);
   }