Keep NaCl plugins used in app background pages alive when active.

ppapi/proxy/plugin_main_nacl.cc

Index: ppapi/proxy/plugin_main_nacl.cc
diff --git a/ppapi/proxy/plugin_main_nacl.cc b/ppapi/proxy/plugin_main_nacl.cc
index f050778227cad4eef35c4f1c26f59fe1a6ccbcbe..46c988a80f3114594b1759c1890add14e32eba22 100644
--- a/ppapi/proxy/plugin_main_nacl.cc
+++ b/ppapi/proxy/plugin_main_nacl.cc
@@ -12,6 +12,7 @@
 // ViewMsgLog et al. functions.
 
 #include "base/command_line.h"
+#include "base/debug/trace_event.h"
 #include "base/message_loop/message_loop.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/thread.h"
@@ -28,6 +29,7 @@
 #include "ppapi/proxy/plugin_globals.h"
 #include "ppapi/proxy/plugin_proxy_delegate.h"
 #include "ppapi/shared_impl/ppb_audio_shared.h"
+#include "ppapi/shared_impl/proxy_lock.h"
 
 #if defined(IPC_MESSAGE_LOG_ENABLED)
 #include "base/containers/hash_tables.h"
@@ -53,6 +55,12 @@ using ppapi::proxy::SerializedHandle;
 
 namespace {
 
+// Interval to check if plugin has been active and report to the browser
+// process. The value is somewhat arbitrary. It should be large enough to
+// minimize computation overhead and small enough to not add exessive latency
+// to detecting idle processes.
+const int kIdleCheckIntervalInSeconds = 5;
+
 // This class manages communication between the plugin and the browser, and
 // manages the PluginDispatcher instances for communication between the plugin
 // and the renderer.
@@ -257,6 +265,24 @@ void PpapiDispatcher::OnPluginDispatcherMessageReceived(
     dispatcher->second->OnMessageReceived(msg);
 }
 
+void CheckActivity(bool last_was_active) {
+  ppapi::ProxyAutoLock lock;
+  if (!PluginGlobals::Get())
+    return;
+
+  bool was_active = PluginGlobals::Get()->plugin_has_been_active();
+  PluginGlobals::Get()->set_plugin_has_been_active(false);
+
+  if (last_was_active != was_active) {
+    PluginGlobals::Get()->GetBrowserSender()->Send(
+        new PpapiHostMsg_IdleStateChange(!was_active));
+  }
+
+  base::MessageLoop::current()->PostDelayedTask(FROM_HERE,
+      base::Bind(&CheckActivity, was_active),
+      base::TimeDelta::FromSeconds(kIdleCheckIntervalInSeconds));
+}
+
 }  // namespace
 
 void PpapiPluginRegisterThreadCreator(
@@ -289,6 +315,9 @@ int PpapiPluginMain() {
   PpapiDispatcher ppapi_dispatcher(io_thread.message_loop_proxy());
   plugin_globals.set_plugin_proxy_delegate(&ppapi_dispatcher);
 
+  base::MessageLoop::current()->PostDelayedTask(FROM_HERE,
+      base::Bind(&CheckActivity, false),
+      base::TimeDelta::FromSeconds(kIdleCheckIntervalInSeconds));
   loop.Run();
 
   return 0;