Pepper: Log in UMA when an interface is used.

content/browser/renderer_host/pepper/browser_ppapi_host_impl.cc

Index: content/browser/renderer_host/pepper/browser_ppapi_host_impl.cc
diff --git a/content/browser/renderer_host/pepper/browser_ppapi_host_impl.cc b/content/browser/renderer_host/pepper/browser_ppapi_host_impl.cc
index e4b3b7693117f9b9acffc25c241d66eec8eefebd..94ddd54d7b3517904d177968ee38ba7c5511b7e0 100644
--- a/content/browser/renderer_host/pepper/browser_ppapi_host_impl.cc
+++ b/content/browser/renderer_host/pepper/browser_ppapi_host_impl.cc
@@ -4,6 +4,7 @@
 
 #include "content/browser/renderer_host/pepper/browser_ppapi_host_impl.h"
 
+#include "base/metrics/sparse_histogram.h"
 #include "content/browser/renderer_host/pepper/pepper_message_filter.h"
 #include "content/browser/tracing/trace_message_filter.h"
 #include "content/common/pepper_renderer_instance_data.h"
@@ -164,6 +165,8 @@ bool BrowserPpapiHostImpl::HostMessageFilter::OnMessageReceived(
   IPC_BEGIN_MESSAGE_MAP(BrowserPpapiHostImpl::HostMessageFilter, msg)
     // Add necessary message handlers here.
     IPC_MESSAGE_HANDLER(PpapiHostMsg_Keepalive, OnKeepalive)
+    IPC_MESSAGE_HANDLER(PpapiHostMsg_LogInterfaceUsage,
+                        OnHostMsgLogInterfaceUsage)
     IPC_MESSAGE_UNHANDLED(handled = ppapi_host_->OnMessageReceived(msg))
   IPC_END_MESSAGE_MAP();
   return handled;
@@ -183,6 +186,11 @@ void BrowserPpapiHostImpl::HostMessageFilter::OnKeepalive() {
     browser_ppapi_host_impl_->OnKeepalive();
 }
 
+void BrowserPpapiHostImpl::HostMessageFilter::OnHostMsgLogInterfaceUsage(
+    int hash) const {
+  UMA_HISTOGRAM_SPARSE_SLOWLY("Pepper.InterfaceUsed", hash);
+}
+
 void BrowserPpapiHostImpl::OnKeepalive() {
   // An instance has been active. The on_keepalive_callback_ will be
   // used to permit the content embedder to handle this, e.g. by tracking