--- a/tools/profiler/core/platform.cpp
+++ b/tools/profiler/core/platform.cpp
@@ -1555,22 +1555,62 @@ StreamTaskTracer(PSLockRef aLock, Splice
   aWriter.EndArray();
 
   aWriter.DoubleProperty(
     "start", static_cast<double>(tasktracer::GetStartTime()));
 #endif
 }
 
 static void
+StreamCategories(SpliceableJSONWriter& aWriter)
+{
+  // Same order as ProfilingStackFrame::Category.
+  // The list of available color names is:
+  // transparent, grey, purple, yellow, orange, lightblue, green, blue, magenta
+  aWriter.Start();
+  aWriter.StringProperty("name", "Idle");
+  aWriter.StringProperty("color", "transparent");
+  aWriter.EndObject();
+  aWriter.Start();
+  aWriter.StringProperty("name", "Other");
+  aWriter.StringProperty("color", "grey");
+  aWriter.EndObject();
+  aWriter.Start();
+  aWriter.StringProperty("name", "Layout");
+  aWriter.StringProperty("color", "purple");
+  aWriter.EndObject();
+  aWriter.Start();
+  aWriter.StringProperty("name", "JavaScript");
+  aWriter.StringProperty("color", "yellow");
+  aWriter.EndObject();
+  aWriter.Start();
+  aWriter.StringProperty("name", "GC / CC");
+  aWriter.StringProperty("color", "orange");
+  aWriter.EndObject();
+  aWriter.Start();
+  aWriter.StringProperty("name", "Network");
+  aWriter.StringProperty("color", "lightblue");
+  aWriter.EndObject();
+  aWriter.Start();
+  aWriter.StringProperty("name", "Graphics");
+  aWriter.StringProperty("color", "green");
+  aWriter.EndObject();
+  aWriter.Start();
+  aWriter.StringProperty("name", "DOM");
+  aWriter.StringProperty("color", "blue");
+  aWriter.EndObject();
+}
+
+static void
 StreamMetaJSCustomObject(PSLockRef aLock, SpliceableJSONWriter& aWriter,
                          bool aIsShuttingDown)
 {
   MOZ_RELEASE_ASSERT(CorePS::Exists() && ActivePS::Exists(aLock));
 
-  aWriter.IntProperty("version", 10);
+  aWriter.IntProperty("version", 11);
 
   // The "startTime" field holds the number of milliseconds since midnight
   // January 1, 1970 GMT. This grotty code computes (Now - (Now -
   // ProcessStartTime)) to convert CorePS::ProcessStartTime() into that form.
   TimeDuration delta = TimeStamp::Now() - CorePS::ProcessStartTime();
   aWriter.DoubleProperty(
     "startTime", static_cast<double>(PR_Now()/1000.0 - delta.ToMilliseconds()));
 
@@ -1578,16 +1618,20 @@ StreamMetaJSCustomObject(PSLockRef aLock
   // absolute time stamp: It's relative to startTime. This is consistent with
   // all other (non-"startTime") times anywhere in the profile JSON.
   if (aIsShuttingDown) {
     aWriter.DoubleProperty("shutdownTime", profiler_time());
   } else {
     aWriter.NullProperty("shutdownTime");
   }
 
+  aWriter.StartArrayProperty("categories");
+  StreamCategories(aWriter);
+  aWriter.EndArray();
+
   if (!NS_IsMainThread()) {
     // Leave the rest of the properties out if we're not on the main thread.
     // At the moment, the only case in which this function is called on a
     // background thread is if we're in a content process and are going to
     // send this profile to the parent process. In that case, the parent
     // process profile's "meta" object already has the rest of the properties,
     // and the parent process profile is dumped on that process's main thread.
     return;