Clarify/fix fullscreen semantics, and add GetScreenSize

ppapi/proxy/ppb_fullscreen_proxy.cc

Index: ppapi/proxy/ppb_fullscreen_proxy.cc
diff --git a/ppapi/proxy/ppb_fullscreen_proxy.cc b/ppapi/proxy/ppb_fullscreen_proxy.cc
index 19c9ead7aba2e5f78bfbd162316093feb8e0e5d4..12848bb8e5367b67eccf640dca287885a765574f 100644
--- a/ppapi/proxy/ppb_fullscreen_proxy.cc
+++ b/ppapi/proxy/ppb_fullscreen_proxy.cc
@@ -35,9 +35,21 @@ PP_Bool SetFullscreen(PP_Instance instance, PP_Bool fullscreen) {
   return result;
 }
 
+PP_Bool GetScreenSize(PP_Instance instance, PP_Size* size) {
+  PluginDispatcher* dispatcher = PluginDispatcher::GetForInstance(instance);
+  if (!dispatcher)
+    return PP_FALSE;
+
+  PP_Bool result = PP_FALSE;
+  dispatcher->Send(new PpapiHostMsg_PPBFullscreen_GetScreenSize(
+      INTERFACE_ID_PPB_FULLSCREEN, instance, &result, size));
+  return result;
+}
+
 const PPB_Fullscreen_Dev fullscreen_interface = {
   &IsFullscreen,
-  &SetFullscreen
+  &SetFullscreen,
+  &GetScreenSize
 };
 
 InterfaceProxy* CreateFullscreenProxy(Dispatcher* dispatcher,
@@ -74,6 +86,8 @@ bool PPB_Fullscreen_Proxy::OnMessageReceived(const IPC::Message& msg) {
                         OnMsgIsFullscreen)
     IPC_MESSAGE_HANDLER(PpapiHostMsg_PPBFullscreen_SetFullscreen,
                         OnMsgSetFullscreen)
+    IPC_MESSAGE_HANDLER(PpapiHostMsg_PPBFullscreen_GetScreenSize,
+                        OnMsgGetScreenSize)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
   // TODO(brettw): handle bad messages!
@@ -91,5 +105,11 @@ void PPB_Fullscreen_Proxy::OnMsgSetFullscreen(PP_Instance instance,
   *result = ppb_fullscreen_target()->SetFullscreen(instance, fullscreen);
 }
 
+void PPB_Fullscreen_Proxy::OnMsgGetScreenSize(PP_Instance instance,
+                                              PP_Bool* result,
+                                              PP_Size* size) {
+  *result = ppb_fullscreen_target()->GetScreenSize(instance, size);
+}
+
 }  // namespace proxy
 }  // namespace pp