WebMessaging: Send transferable ArrayBuffers by copy-and-neuter semantics

third_party/WebKit/Source/bindings/templates/methods.cpp.tmpl

 {% from 'utilities.cpp.tmpl' import declare_enum_validation_variable, v8_value_to_local_cpp_value %}
 
 {##############################################################################}
 {% macro generate_method(method, world_suffix) %}
 static void {{method.name}}{{method.overload_index}}Method{{world_suffix}}(const v8::FunctionCallbackInfo<v8::Value>& info)
 {% filter format_remove_duplicates([
     'ExceptionState exceptionState',
     'ScriptState* scriptState = ']) %}
 {
     {% set define_exception_state -%}
@@ skipping 417 matching lines @@
 
 {##############################################################################}
 {% macro generate_post_message_impl(method) %}
 static void postMessageImpl(const char* interfaceName, {{cpp_class}}* instance, const v8::FunctionCallbackInfo<v8::Value>& info)
 {
     ExceptionState exceptionState(info.GetIsolate(), ExceptionState::ExecutionContext, interfaceName, "postMessage");
     if (UNLIKELY(info.Length() < {{method.number_of_required_arguments}})) {
         exceptionState.throwTypeError(ExceptionMessages::notEnoughArguments({{method.number_of_required_arguments}}, info.Length()));
         return;
     }
+
     Transferables transferables;
     if (info.Length() > 1) {
         const int transferablesArgIndex = 1;
         if (!SerializedScriptValue::extractTransferables(info.GetIsolate(), info[transferablesArgIndex], transferablesArgIndex, transferables, exceptionState)) {
             return;
         }
     }
-    RefPtr<SerializedScriptValue> message = SerializedScriptValue::serialize(info.GetIsolate(), info[0], &transferables, nullptr, exceptionState);
-    if (exceptionState.hadException())
-        return;
+
+    RefPtr<SerializedScriptValue> message;
+    if (instance->canTransferArrayBuffer()) {
+        // This instance supports sending array buffers by move semantics.
+        message = SerializedScriptValue::serialize(info.GetIsolate(), info[0], &transferables, nullptr, exceptionState);
+        if (exceptionState.hadException())
+            return;
+    } else {
+        // This instance doesn't support sending array buffers by move
+        // semantics. Emulate it by copy-and-neuter semantics that sends array
+        // buffers by copy semantics and then neuters the original array
+        // buffers.
+
+        // Clear references to array buffers from transferables so that the
+        // serializer can consider the array buffers as non-transferable and
+        // copy them into the message.
+        ArrayBufferArray transferableArrayBuffers = transferables.arrayBuffers;
+        transferables.arrayBuffers.clear();
+        message = SerializedScriptValue::serialize(info.GetIsolate(), info[0], &transferables, nullptr, exceptionState);
+        if (exceptionState.hadException())
+            return;
+
+        // Neuter the original array buffers on the sender context.
+        SerializedScriptValue::transferArrayBufferContents(info.GetIsolate(), transferableArrayBuffers, exceptionState);
+        if (exceptionState.hadException())
+            return;
+    }
+
     // FIXME: Only pass context/exceptionState if instance really requires it.
     ExecutionContext* context = currentExecutionContext(info.GetIsolate());
     instance->postMessage(context, message.release(), transferables.messagePorts, exceptionState);
 }
 {% endmacro %}
 
 
 {##############################################################################}
 {% macro method_callback(method, world_suffix) %}
 void {{method.name}}MethodCallback{{world_suffix}}(const v8::FunctionCallbackInfo<v8::Value>& info)
@@ skipping 194 matching lines @@
                           if method.overloads else
                           method.runtime_enabled_function) %}
 const V8DOMConfiguration::MethodConfiguration {{method.name}}MethodConfiguration = {{method_configuration(method)}};
 V8DOMConfiguration::installMethod(isolate, world, v8::Local<v8::Object>(), prototypeObject, interfaceObject, signature, {{method.name}}MethodConfiguration);
 {% endfilter %}{# runtime_enabled() #}
 {% endfilter %}{# exposed() #}
 {% endfilter %}{# secure_context() #}
 {% endfor %}
 {% endif %}
 {%- endmacro %}