Allow MessageFilters to restrict listening to specific message classes

content/browser/histogram_message_filter.cc

Index: content/browser/histogram_message_filter.cc
diff --git a/content/browser/histogram_message_filter.cc b/content/browser/histogram_message_filter.cc
index f44accdc3499dcef70226ce10772dbdcadbd79ce..92971f566e3c22ddf3cd4d8b5870c73e6a49c915 100644
--- a/content/browser/histogram_message_filter.cc
+++ b/content/browser/histogram_message_filter.cc
@@ -13,8 +13,15 @@
 #include "content/public/common/content_switches.h"
 
 namespace content {
+namespace {
+const uint32 kFilteredMessageClasses[] = {
+  ChildProcessMsgStart,
+};
+}  // namespace
 
-HistogramMessageFilter::HistogramMessageFilter() {}
+HistogramMessageFilter::HistogramMessageFilter()
+    : BrowserMessageFilter(
+          kFilteredMessageClasses, arraysize(kFilteredMessageClasses)) {}
 
 bool HistogramMessageFilter::OnMessageReceived(const IPC::Message& message,
                                               bool* message_was_ok) {