diff --git a/runtime/platform/text_buffer.cc b/runtime/platform/text_buffer.cc
index b9c6ac7515b..1536dac13b3 100644
--- a/runtime/platform/text_buffer.cc
+++ b/runtime/platform/text_buffer.cc
@@ -48,6 +48,14 @@ void TextBuffer::AddChar(char ch) {
 }
 
 
+void TextBuffer::AddRaw(const uint8_t* buffer,
+                        intptr_t buffer_length) {
+  EnsureCapacity(buffer_length);
+  memmove(&buf_[msg_len_], buffer, buffer_length);
+  msg_len_ += buffer_length;
+  buf_[msg_len_] = '\0';
+}
+
 intptr_t TextBuffer::Printf(const char* format, ...) {
   va_list args;
   va_start(args, format);
diff --git a/runtime/platform/text_buffer.h b/runtime/platform/text_buffer.h
index f8f0c2fcc8c..1908ecb05cf 100644
--- a/runtime/platform/text_buffer.h
+++ b/runtime/platform/text_buffer.h
@@ -23,6 +23,8 @@ class TextBuffer : ValueObject {
   void EscapeAndAddCodeUnit(uint32_t cu);
   void AddString(const char* s);
   void AddEscapedString(const char* s);
+  void AddRaw(const uint8_t* buffer,
+              intptr_t buffer_length);
 
   void Clear();
 
diff --git a/runtime/vm/dart_api_impl.cc b/runtime/vm/dart_api_impl.cc
index 8f3cb9764c5..12a7fdb29e5 100644
--- a/runtime/vm/dart_api_impl.cc
+++ b/runtime/vm/dart_api_impl.cc
@@ -5890,8 +5890,7 @@ static void DataStreamToConsumer(Dart_StreamConsumer consumer,
 
 static bool StreamTraceEvents(Dart_StreamConsumer consumer,
                               void* user_data,
-                              JSONStream* js,
-                              bool insert_comma) {
+                              JSONStream* js) {
   ASSERT(js != NULL);
   // Steal output from JSONStream.
   char* output = NULL;
@@ -5909,13 +5908,8 @@ static bool StreamTraceEvents(Dart_StreamConsumer consumer,
   // Replace the ']' with the null character.
   output[output_length - 1] = '\0';
   char* start = &output[1];
-  if (insert_comma) {
-    output[0] = ',';
-    start = &output[0];
-  } else {
-    // We are skipping the '['.
-    output_length -= 1;
-  }
+  // We are skipping the '['.
+  output_length -= 1;
 
   DataStreamToConsumer(consumer,
                        user_data,
@@ -5952,7 +5946,7 @@ DART_EXPORT bool Dart_TimelineGetTrace(Dart_StreamConsumer consumer,
   IsolateTimelineEventFilter filter(isolate->main_port());
   timeline_recorder->PrintTraceEvent(&js, &filter);
   StartStreamToConsumer(consumer, user_data, "timeline");
-  bool success = StreamTraceEvents(consumer, user_data, &js, false);
+  bool success = StreamTraceEvents(consumer, user_data, &js);
   FinishStreamToConsumer(consumer, user_data, "timeline");
   return success;
 }
@@ -5989,17 +5983,12 @@ DART_EXPORT bool Dart_GlobalTimelineGetTrace(Dart_StreamConsumer consumer,
     return false;
   }
   Timeline::ReclaimCachedBlocksFromThreads();
+  bool success = false;
   JSONStream js;
   TimelineEventFilter filter;
   timeline_recorder->PrintTraceEvent(&js, &filter);
   StartStreamToConsumer(consumer, user_data, "timeline");
-  bool success = false;
-  if (Timeline::get_get_timeline_cb() != NULL) {
-    if (Timeline::get_get_timeline_cb()(consumer, user_data)) {
-      success = true;
-    }
-  }
-  if (StreamTraceEvents(consumer, user_data, &js, success)) {
+  if (StreamTraceEvents(consumer, user_data, &js)) {
     success = true;
   }
   FinishStreamToConsumer(consumer, user_data, "timeline");
diff --git a/runtime/vm/dart_api_impl_test.cc b/runtime/vm/dart_api_impl_test.cc
index 6c6fb8f9a92..4be3fa90039 100644
--- a/runtime/vm/dart_api_impl_test.cc
+++ b/runtime/vm/dart_api_impl_test.cc
@@ -9827,7 +9827,7 @@ TEST_CASE(Timeline_Dart_EmbedderTimelineGetTimeline) {
   bool success = Dart_GlobalTimelineGetTrace(AppendStreamConsumer, &data);
   EXPECT(success);
 
-  EXPECT_SUBSTRING("HELLO FROM EMBEDDER,{\"name\":\"testDurationEvent\"",
+  EXPECT_SUBSTRING("}},HELLO FROM EMBEDDER",
                    data.buffer);
 
   // Free buffer allocated by AppendStreamConsumer
diff --git a/runtime/vm/json_stream.cc b/runtime/vm/json_stream.cc
index a68d87d8553..a721c7e9bb0 100644
--- a/runtime/vm/json_stream.cc
+++ b/runtime/vm/json_stream.cc
@@ -20,6 +20,23 @@ namespace dart {
 
 #ifndef PRODUCT
 
+void AppendJSONStreamConsumer(Dart_StreamConsumer_State state,
+                              const char* stream_name,
+                              const uint8_t* buffer,
+                              intptr_t buffer_length,
+                              void* user_data) {
+  if ((state == Dart_StreamConsumer_kStart) ||
+      (state == Dart_StreamConsumer_kFinish)) {
+    // Ignore.
+    return;
+  }
+  ASSERT(state == Dart_StreamConsumer_kData);
+  JSONStream* js = reinterpret_cast<JSONStream*>(user_data);
+  ASSERT(js != NULL);
+  js->AppendSerializedObject(buffer, buffer_length);
+}
+
+
 DECLARE_FLAG(bool, trace_service);
 
 JSONStream::JSONStream(intptr_t buf_size)
@@ -263,6 +280,11 @@ void JSONStream::AppendSerializedObject(const char* serialized_object) {
 }
 
 
+void JSONStream::AppendSerializedObject(const uint8_t* buffer,
+                                        intptr_t buffer_length) {
+  buffer_.AddRaw(buffer, buffer_length);
+}
+
 void JSONStream::AppendSerializedObject(const char* property_name,
                                         const char* serialized_object) {
   PrintCommaIfNeeded();
diff --git a/runtime/vm/json_stream.h b/runtime/vm/json_stream.h
index 6c4f23e32bc..5b020b0d660 100644
--- a/runtime/vm/json_stream.h
+++ b/runtime/vm/json_stream.h
@@ -55,6 +55,12 @@ enum JSONRpcErrorCode {
   kIsolateMustBeRunnable   = 105,
 };
 
+// Expected that user_data is a JSONStream*.
+void AppendJSONStreamConsumer(Dart_StreamConsumer_State state,
+                              const char* stream_name,
+                              const uint8_t* buffer,
+                              intptr_t buffer_length,
+                              void* user_data);
 
 class JSONStream : ValueObject {
  public:
@@ -129,6 +135,12 @@ class JSONStream : ValueObject {
   // Append |serialized_object| to the stream.
   void AppendSerializedObject(const char* serialized_object);
 
+  void PrintCommaIfNeeded();
+
+  // Append |buffer| to the stream.
+  void AppendSerializedObject(const uint8_t* buffer,
+                              intptr_t buffer_length);
+
   // Append |serialized_object| to the stream with |property_name|.
   void AppendSerializedObject(const char* property_name,
                               const char* serialized_object);
@@ -196,7 +208,6 @@ class JSONStream : ValueObject {
                      const TimelineEventBlock* timeline_event_block);
   void PrintPropertyVM(const char* name, bool ref = true);
   void PrintPropertyName(const char* name);
-  void PrintCommaIfNeeded();
   bool NeedComma();
 
   bool AddDartString(const String& s, intptr_t offset, intptr_t count);
diff --git a/runtime/vm/json_test.cc b/runtime/vm/json_test.cc
index 7c5b49f81a1..e8c4f5d959a 100644
--- a/runtime/vm/json_test.cc
+++ b/runtime/vm/json_test.cc
@@ -315,6 +315,33 @@ TEST_CASE(JSON_JSONStream_Params) {
   EXPECT(!js.ParamIs("dog", "banana"));
 }
 
+
+TEST_CASE(JSON_JSONStream_AppendJSONStreamConsumer) {
+  JSONStream js;
+
+  {
+    JSONObject obj(&js);
+    {
+      JSONArray arr(&obj, "test");
+      const char* test_data = "{a, b, c},";
+      AppendJSONStreamConsumer(Dart_StreamConsumer_kData, "",
+                               reinterpret_cast<const uint8_t*>(&test_data[0]),
+                               strlen(test_data),
+                               &js);
+      AppendJSONStreamConsumer(Dart_StreamConsumer_kData, "",
+                               reinterpret_cast<const uint8_t*>(&test_data[0]),
+                               strlen(test_data),
+                               &js);
+      AppendJSONStreamConsumer(Dart_StreamConsumer_kData, "",
+                               reinterpret_cast<const uint8_t*>(&test_data[0]),
+                               strlen(test_data) - 1,
+                               &js);
+    }
+  }
+
+  EXPECT_STREQ("{\"test\":[{a, b, c},{a, b, c},{a, b, c}]}", js.ToCString());
+}
+
 #endif  // !PRODUCT
 
 }  // namespace dart
diff --git a/runtime/vm/timeline.cc b/runtime/vm/timeline.cc
index 4072d806894..cd0b0fdb8ef 100644
--- a/runtime/vm/timeline.cc
+++ b/runtime/vm/timeline.cc
@@ -1027,6 +1027,14 @@ void TimelineEventRecorder::ThreadBlockCompleteEvent(TimelineEvent* event) {
 }
 
 
+void TimelineEventRecorder::PrintEmbedderJSONEvents(JSONStream* events) {
+  if (Timeline::get_get_timeline_cb() != NULL) {
+    events->PrintCommaIfNeeded();
+    Timeline::get_get_timeline_cb()(AppendJSONStreamConsumer, events);
+  }
+}
+
+
 void TimelineEventRecorder::WriteTo(const char* directory) {
   if (!FLAG_support_service) {
     return;
@@ -1166,6 +1174,7 @@ void TimelineEventRingRecorder::PrintJSON(JSONStream* js,
     JSONArray events(&topLevel, "traceEvents");
     PrintJSONMeta(&events);
     PrintJSONEvents(&events, filter);
+    PrintEmbedderJSONEvents(js);
   }
 }
 
@@ -1177,6 +1186,7 @@ void TimelineEventRingRecorder::PrintTraceEvent(JSONStream* js,
   }
   JSONArray events(js);
   PrintJSONEvents(&events, filter);
+  PrintEmbedderJSONEvents(js);
 }
 
 
@@ -1299,6 +1309,7 @@ void TimelineEventEndlessRecorder::PrintJSON(JSONStream* js,
     JSONArray events(&topLevel, "traceEvents");
     PrintJSONMeta(&events);
     PrintJSONEvents(&events, filter);
+    PrintEmbedderJSONEvents(js);
   }
 }
 
@@ -1311,6 +1322,7 @@ void TimelineEventEndlessRecorder::PrintTraceEvent(
   }
   JSONArray events(js);
   PrintJSONEvents(&events, filter);
+  PrintEmbedderJSONEvents(js);
 }
 
 
diff --git a/runtime/vm/timeline.h b/runtime/vm/timeline.h
index 3bd32dd24c2..9887aff721f 100644
--- a/runtime/vm/timeline.h
+++ b/runtime/vm/timeline.h
@@ -678,6 +678,7 @@ class TimelineEventRecorder {
   void PrintJSONMeta(JSONArray* array) const;
   TimelineEvent* ThreadBlockStartEvent();
   void ThreadBlockCompleteEvent(TimelineEvent* event);
+  void PrintEmbedderJSONEvents(JSONStream* events);
 
   Mutex lock_;
   uintptr_t async_id_;