PPAPI: Make Messaging not PostTask and copy when out-of-process.

webkit/plugins/ppapi/message_channel.cc

Index: webkit/plugins/ppapi/message_channel.cc
diff --git a/webkit/plugins/ppapi/message_channel.cc b/webkit/plugins/ppapi/message_channel.cc
index 646b822201ca6e640262c3cd96ee892d2f8a82c3..5f4dce27b353eee654eda5da39b98b50f991ec92 100644
--- a/webkit/plugins/ppapi/message_channel.cc
+++ b/webkit/plugins/ppapi/message_channel.cc
@@ -24,6 +24,7 @@
 #include "v8/include/v8.h"
 #include "webkit/plugins/ppapi/host_array_buffer_var.h"
 #include "webkit/plugins/ppapi/npapi_glue.h"
+#include "webkit/plugins/ppapi/plugin_module.h"
 #include "webkit/plugins/ppapi/ppapi_plugin_instance.h"
 
 using ppapi::ArrayBufferVar;
@@ -330,7 +331,8 @@ MessageChannel::MessageChannel(PluginInstance* instance)
     : instance_(instance),
       passthrough_object_(NULL),
       np_object_(NULL),
-      ALLOW_THIS_IN_INITIALIZER_LIST(weak_ptr_factory_(this)) {
+      ALLOW_THIS_IN_INITIALIZER_LIST(weak_ptr_factory_(this)),
+      queue_js_messages_(true) {
   // Now create an NPObject for receiving calls to postMessage. This sets the
   // reference count to 1.  We release it in the destructor.
   NPObject* obj = WebBindings::createObject(NULL, &message_channel_class);
@@ -358,11 +360,50 @@ void MessageChannel::PostMessageToJavaScript(PP_Var message_data) {
   WebSerializedScriptValue serialized_val =
       WebSerializedScriptValue::serialize(v8_val);
 
+  if (instance_->module()->IsProxied()) {
+    if (queue_js_messages_) {
+      // We can't just PostTask here; the messages would arrive out of
+      // order. Instead, we queue them up until we're ready to post
+      // them.
+      early_message_queue_.push_back(serialized_val);
+    } else {
+      // The proxy sent an asynchronous message, so the plugin is already
+      // unblocked. Therefore, there's no need to PostTask.
+      DCHECK(early_message_queue_.size() == 0);
+      PostMessageToJavaScriptImpl(serialized_val);
+    }
+  } else {
+    MessageLoop::current()->PostTask(
+        FROM_HERE,
+        base::Bind(&MessageChannel::PostMessageToJavaScriptImpl,
+                   weak_ptr_factory_.GetWeakPtr(),
+                   serialized_val));
+  }
+}
+
+void MessageChannel::EndQueueingJavaScriptMessages() {
+  // We PostTask here instead of draining the message queue directly
+  // since we haven't finished initializing the WebPluginImpl yet, so
+  // the plugin isn't available in the DOM.
+  DCHECK(queue_js_messages_);

[dmichael (off chromium), 2012/12/11 18:55:55]

Do you think there's any chance of calling QueueJavaScriptMessages before the
Drain... task runs?

[teravest, 2012/12/11 21:32:12]

I cleaned this up by making an enum of the possible states. We can now cancel a
pending drain task.

   MessageLoop::current()->PostTask(
       FROM_HERE,
-      base::Bind(&MessageChannel::PostMessageToJavaScriptImpl,
-                 weak_ptr_factory_.GetWeakPtr(),
-                 serialized_val));
+      base::Bind(&MessageChannel::DrainEarlyMessageQueue,
+                 weak_ptr_factory_.GetWeakPtr()));
+}
+
+void MessageChannel::QueueJavaScriptMessages() {
+  DCHECK(!queue_js_messages_);
+  queue_js_messages_ = true;
+}
+
+void MessageChannel::DrainEarlyMessageQueue() {
+  DCHECK(queue_js_messages_);
+  while (!early_message_queue_.empty()) {
+    PostMessageToJavaScriptImpl(early_message_queue_.front());
+    early_message_queue_.pop_front();
+  }
+  queue_js_messages_ = false;
 }
 
 void MessageChannel::PostMessageToJavaScriptImpl(
@@ -398,13 +439,20 @@ void MessageChannel::PostMessageToJavaScriptImpl(
 }
 
 void MessageChannel::PostMessageToNative(PP_Var message_data) {
-  // Make a copy of the message data for the Task we will run.
-  PP_Var var_copy(CopyPPVar(message_data));
+  if (instance_->module()->IsProxied()) {
+    // In the proxied case, the copy will happen via serializiation, and the
+    // message is asynchronous. Therefore there's no need to copy the Var, nor
+    // to PostTask.
+    PostMessageToNativeImpl(message_data);
+  } else {
+    // Make a copy of the message data for the Task we will run.
+    PP_Var var_copy(CopyPPVar(message_data));
 
-  MessageLoop::current()->PostTask(FROM_HERE,
-      base::Bind(&MessageChannel::PostMessageToNativeImpl,
-                 weak_ptr_factory_.GetWeakPtr(),
-                 var_copy));
+    MessageLoop::current()->PostTask(FROM_HERE,
+        base::Bind(&MessageChannel::PostMessageToNativeImpl,
+                   weak_ptr_factory_.GetWeakPtr(),
+                   var_copy));
+  }
 }
 
 void MessageChannel::PostMessageToNativeImpl(PP_Var message_data) {