Bug 1264820 - Measure IPC reply size in telemetry (r=mccr8)

ipc/glue/MessageChannel.cpp

@@ -759,7 +759,7 @@ MessageChannel::Send(Message* aMsg)
 {
     if (aMsg->capacity() >= kMinTelemetryMessageSize) {
         Telemetry::Accumulate(Telemetry::IPC_MESSAGE_SIZE,
-                              nsCString(aMsg->name()), aMsg->capacity());
+                              nsDependentCString(aMsg->name()), aMsg->capacity());
     }
 
     CxxStackFrame frame(*this, OUT_MESSAGE, aMsg);
@@ -1059,7 +1059,7 @@ MessageChannel::Send(Message* aMsg, Message* aReply)
 {
     if (aMsg->capacity() >= kMinTelemetryMessageSize) {
         Telemetry::Accumulate(Telemetry::IPC_MESSAGE_SIZE,
-                              nsCString(aMsg->name()), aMsg->capacity());
+                              nsDependentCString(aMsg->name()), aMsg->capacity());
     }
 
     nsAutoPtr<Message> msg(aMsg);
@@ -1244,6 +1244,10 @@ MessageChannel::Send(Message* aMsg, Message* aReply)
     MOZ_RELEASE_ASSERT(reply->is_sync());
 
     *aReply = Move(*reply);
+    if (aReply->size() >= kMinTelemetryMessageSize) {
+        Telemetry::Accumulate(Telemetry::IPC_REPLY_SIZE,
+                              nsDependentCString(aMsg->name()), aReply->capacity());
+    }
     return true;
 }
 

toolkit/components/telemetry/Histograms.json

@@ -10521,6 +10521,16 @@
     "keyed": true,
     "description": "Measures the size of IPC messages by message name"
   },
+  "IPC_REPLY_SIZE": {
+    "alert_emails": ["wmccloskey@mozilla.com"],
+    "bug_numbers": [1264820],
+    "expires_in_version": "55",
+    "kind": "exponential",
+    "high": 8000000,
+    "n_buckets": 50,
+    "keyed": true,
+    "description": "Measures the size of IPC messages by message name"
+  },
   "MESSAGE_MANAGER_MESSAGE_SIZE": {
     "alert_emails": ["wmccloskey@mozilla.com"],
     "bug_numbers": [1260908],