Add a |scope| argument to TRACE_EVENT_INSTANT* and require its presence.

base/debug/trace_event_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/debug/trace_event_impl.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/debug/leak_annotations.h"
@@ skipping 390 matching lines @@
     *out += arg_names_[i];
     *out += "\":";
     AppendValueAsJSON(arg_types_[i], arg_values_[i], out);
   }
   *out += "}";
 
   // If id_ is set, print it out as a hex string so we don't loose any
   // bits (it might be a 64-bit pointer).
   if (flags_ & TRACE_EVENT_FLAG_HAS_ID)
     StringAppendF(out, ",\"id\":\"%" PRIx64 "\"", static_cast<uint64>(id_));
+
+  // Instant events also output their scope.
+  if (phase_ == TRACE_EVENT_PHASE_INSTANT) {
+    char scope = '?';
+    switch (flags_ & TRACE_EVENT_FLAG_SCOPE_MASK) {
+      case TRACE_EVENT_SCOPE_GLOBAL:
+        scope = TRACE_EVENT_SCOPE_NAME_GLOBAL;
+        break;
+
+      case TRACE_EVENT_SCOPE_PROCESS:
+        scope = TRACE_EVENT_SCOPE_NAME_PROCESS;
+        break;
+
+      case TRACE_EVENT_SCOPE_THREAD:
+        scope = TRACE_EVENT_SCOPE_NAME_THREAD;
+        break;
+    }
+    StringAppendF(out, ",\"s\":\"%c\"", scope);
+  }
+
   *out += "}";
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 //
 // TraceResultBuffer
 //
 ////////////////////////////////////////////////////////////////////////////////
 
 TraceResultBuffer::OutputCallback
@@ skipping 816 matching lines @@
         0,                       // num_args
         NULL,                    // arg_names
         NULL,                    // arg_types
         NULL,                    // arg_values
         TRACE_EVENT_FLAG_NONE);  // flags
   }
 }
 
 }  // namespace trace_event_internal