Pepper: Log in UMA when an interface is used.

ppapi/proxy/interface_list.cc

Index: ppapi/proxy/interface_list.cc
diff --git a/ppapi/proxy/interface_list.cc b/ppapi/proxy/interface_list.cc
index 79789d70ace37d9fc95b62b3a6bb4790289e589b..6c202fa3ea67de54219073ab3ed23773082f285e 100644
--- a/ppapi/proxy/interface_list.cc
+++ b/ppapi/proxy/interface_list.cc
@@ -4,6 +4,7 @@
 
 #include "ppapi/proxy/interface_list.h"
 
+#include "base/hash.h"
 #include "base/lazy_instance.h"
 #include "base/memory/singleton.h"
 #include "ppapi/c/dev/ppb_alarms_dev.h"
@@ -104,6 +105,8 @@
 #include "ppapi/c/trusted/ppb_file_chooser_trusted.h"
 #include "ppapi/c/trusted/ppb_url_loader_trusted.h"
 #include "ppapi/proxy/interface_proxy.h"
+#include "ppapi/proxy/plugin_globals.h"
+#include "ppapi/proxy/ppapi_messages.h"
 #include "ppapi/proxy/ppb_audio_proxy.h"
 #include "ppapi/proxy/ppb_broker_proxy.h"
 #include "ppapi/proxy/ppb_buffer_proxy.h"
@@ -315,15 +318,26 @@ InterfaceProxy::Factory InterfaceList::GetFactoryForID(ApiID id) const {
   return id_to_factory_[index];
 }
 
-const void* InterfaceList::GetInterfaceForPPB(const std::string& name) const {
-  NameToInterfaceInfoMap::const_iterator found =
+const void* InterfaceList::GetInterfaceForPPB(const std::string& name) {
+  NameToInterfaceInfoMap::iterator found =
       name_to_browser_info_.find(name);
   if (found == name_to_browser_info_.end())
     return NULL;
 
   if (g_process_global_permissions.Get().HasPermission(
-          found->second.required_permission))
+          found->second.required_permission)) {
+    // Only log interface use once per plugin.
+    if (!found->second.interface_logged) {
+      uint32 data = base::Hash(name.c_str(), name.size());
+      // Strip off the signed bit because UMA doesn't support negative values,
+      // but takes a signed int as input.
+      int hash = static_cast<int>(data & 0x7fffffff);

[Alexei Svitkine (slow), 2014/02/04 18:30:43]

Is base::Hash() guaranteed to never change implementation?

Can you add a test somewhere that would break when it does? (e.g. that checks
that base::Hash() produces one of the expected values for a given input - i.e.
use one or a few of the entries in histograms.xml as test cases?

This way, we can avoid any nasty surprises.

+      PluginGlobals::Get()->GetBrowserSender()->Send(
+          new PpapiHostMsg_LogInterfaceUsage(hash));
+      found->second.interface_logged = true;
+    }
     return found->second.iface;
+  }
   return NULL;
 }