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

webkit/plugins/ppapi/message_channel.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "webkit/plugins/ppapi/message_channel.h"
 
 #include <cstdlib>
 #include <string>
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/message_loop.h"
 #include "ppapi/shared_impl/ppapi_globals.h"
 #include "ppapi/shared_impl/var.h"
 #include "ppapi/shared_impl/var_tracker.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebBindings.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebDocument.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebDOMMessageEvent.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebElement.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebFrame.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebNode.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebPluginContainer.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebSerializedScriptValue.h"
 #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;
 using ppapi::PpapiGlobals;
 using ppapi::StringVar;
 using WebKit::WebBindings;
 using WebKit::WebElement;
 using WebKit::WebDOMEvent;
 using WebKit::WebDOMMessageEvent;
 using WebKit::WebPluginContainer;
@@ skipping 286 matching lines @@
 // MessageChannel --------------------------------------------------------------
 MessageChannel::MessageChannelNPObject::MessageChannelNPObject() {
 }
 
 MessageChannel::MessageChannelNPObject::~MessageChannelNPObject() {}
 
 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)),
+      did_create_finished_(false) {
   // 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);
   DCHECK(obj);
   np_object_ = static_cast<MessageChannel::MessageChannelNPObject*>(obj);
   np_object_->message_channel = weak_ptr_factory_.GetWeakPtr();
 }
 
 void MessageChannel::PostMessageToJavaScript(PP_Var message_data) {
   // Serialize the message data.
   v8::HandleScope scope;
   // Because V8 is probably not on the stack for Native->JS calls, we need to
   // enter the appropriate context for the plugin.
   v8::Local<v8::Context> context =
       instance_->container()->element().document().frame()->
           mainWorldScriptContext();
   v8::Context::Scope context_scope(context);
 
   v8::Local<v8::Value> v8_val;
   if (!PPVarToV8Value(message_data, &v8_val)) {
     NOTREACHED();
     return;
   }
 
   WebSerializedScriptValue serialized_val =
       WebSerializedScriptValue::serialize(v8_val);
 
+  if (instance_->module()->IsProxied()) {
+    // The proxy sent an asynchronous message, so the plugin is already
+    //  unblocked. Therefore, there's no need to PostTask.

[dmichael (off chromium), 2012/12/10 22:02:52]

This comment probably belongs in the first branch of the if below now

[teravest, 2012/12/10 22:30:59]

Done.

+    if (did_create_finished_) {
+      DCHECK(early_message_queue_.size() == 0);
+      PostMessageToJavaScriptImpl(serialized_val);
+    } else {
+      early_message_queue_.push_back(serialized_val);

[dmichael (off chromium), 2012/12/10 22:02:52]

Probably worth a brief comment why we have to defer sending (here or on the
member in the header)

And a comment here about why we can't just PostTask

[teravest, 2012/12/10 22:30:59]

Done.

+    }
+  } else {
+    MessageLoop::current()->PostTask(
+        FROM_HERE,
+        base::Bind(&MessageChannel::PostMessageToJavaScriptImpl,
+                   weak_ptr_factory_.GetWeakPtr(),
+                   serialized_val));
+  }
+}
+
+void MessageChannel::DidCreateFinished() {
+  // 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.
   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::DrainEarlyMessageQueue() {

[dmichael (off chromium), 2012/12/10 22:02:52]

Might be worth doing:
DCHECK(!did_create_finished_);

[teravest, 2012/12/10 22:30:59]

Done.

+  while (!early_message_queue_.empty()) {
+    PostMessageToJavaScriptImpl(early_message_queue_.front());
+    early_message_queue_.pop_front();

[dmichael (off chromium), 2012/12/10 22:02:52]

If there's any chance of re-entry, you'd probably want to do something more
like:
WebSerializedScriptValue val = early_message_queue_.front();
early_message_queue_.pop_front();
PostMessageToJavaScriptImpl(val);

...it's unlikely, but it actually could happen for trusted in-process plugins,
if they do some sync scripting call in their JavaScript message event handler.

[teravest, 2012/12/10 22:30:59]

I think it's safe as is...

On 2012/12/10 22:02:52, dmichael wrote:

[dmichael (off chromium), 2012/12/10 22:49:47]

Yes, I wasn't thinking straight; the problem I was imagining would happen if
there was re-entry in to *this* method, which should never happen.

+  }
+  did_create_finished_ = true;
 }
 
 void MessageChannel::PostMessageToJavaScriptImpl(
     const WebSerializedScriptValue& message_data) {
   DCHECK(instance_);
 
   WebPluginContainer* container = instance_->container();
   // It's possible that container() is NULL if the plugin has been removed from
   // the DOM (but the PluginInstance is not destroyed yet).
   if (!container)
@@ skipping 15 matching lines @@
   //      http://www.whatwg.org/specs/web-apps/current-work/multipage/comms.html
   //     This currently behaves like Web Workers. On Firefox, Chrome, and Safari
   //     at least, postMessage on Workers does not provide the origin or source.
   //     TODO(dmichael):  Add origin if we change to a more iframe-like origin
   //                      policy (see crbug.com/81537)
 
   container->element().dispatchEvent(msg_event);
 }
 
 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) {
   instance_->HandleMessage(message_data);
 }
 
 MessageChannel::~MessageChannel() {
   WebBindings::releaseObject(np_object_);
   if (passthrough_object_)
     WebBindings::releaseObject(passthrough_object_);
@@ skipping 10 matching lines @@
   // invokes:
   //   SetPassthroughObject(passthrough_object());
   if (passthrough_object_)
     WebBindings::releaseObject(passthrough_object_);
 
   passthrough_object_ = passthrough;
 }
 
 }  // namespace ppapi
 }  // namespace webkit