HTML MessagePort as mojo::MessagePipeHandle

content/common/fileapi/webblob_messages.h

 // 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.
 
 // IPC messages for HTML5 Blob and Stream.
 // Multiply-included message file, hence no include guard.
 
 #include <stddef.h>
 
 #include <set>
@@ skipping 36 matching lines @@
   IPC_STRUCT_TRAITS_MEMBER(time_file_modified)
 IPC_STRUCT_TRAITS_END()
 
 // This message is to tell the browser that we will be building a blob. The
 // DataElements are used to:
 // * describe & transport non-memory resources (blobs, files, etc)
 // * describe the size of memory items
 // * 'shortcut' transport the memory up to the IPC limit so the browser can use
 //   it if it's not currently full.
 // See https://bit.ly/BlobStorageRefactor
-IPC_MESSAGE_CONTROL4(BlobStorageMsg_RegisterBlob,
-                     std::string /* uuid */,
-                     std::string /* content_type */,
-                     std::string /* content_disposition */,
-                     std::vector<storage::DataElement> /* item_descriptions */)
+//
+// NOTE: This message is synchronous to ensure that the browser is aware of the
+// UUID before the UUID is passed to another process. This protects against a
+// race condition in which the browser could be asked about a UUID that doesn't
+// yet exist from its perspective.
+//
+IPC_SYNC_MESSAGE_CONTROL4_0(
+    BlobStorageMsg_RegisterBlob,
+    std::string /* uuid */,
+    std::string /* content_type */,
+    std::string /* content_disposition */,
+    std::vector<storage::DataElement> /* item_descriptions */)
 
 IPC_MESSAGE_CONTROL4(
     BlobStorageMsg_RequestMemoryItem,
     std::string /* uuid */,
     std::vector<storage::BlobItemBytesRequest> /* requests */,
     std::vector<base::SharedMemoryHandle> /* memory_handles */,
     std::vector<IPC::PlatformFileForTransit> /* file_handles */)
 
 IPC_MESSAGE_CONTROL2(
     BlobStorageMsg_MemoryItemResponse,
     std::string /* uuid */,
     std::vector<storage::BlobItemBytesResponse> /* responses */)
 
 IPC_MESSAGE_CONTROL2(BlobStorageMsg_SendBlobStatus,
                      std::string /* uuid */,
                      storage::BlobStatus /* code */)
 
 IPC_MESSAGE_CONTROL1(BlobHostMsg_IncrementRefCount,
                      std::string /* uuid */)
 IPC_MESSAGE_CONTROL1(BlobHostMsg_DecrementRefCount,
                      std::string /* uuid */)
-IPC_MESSAGE_CONTROL2(BlobHostMsg_RegisterPublicURL,
-                     GURL,
-                     std::string /* uuid */)
+// NOTE: This message is synchronous to ensure that the browser is aware of the
+// URL before the URL is passed to another process. This protects against a
+// race condition in which the browser could be asked to load an URL that
+// doesn't yet exist from its perspective.
+IPC_SYNC_MESSAGE_CONTROL2_0(BlobHostMsg_RegisterPublicURL,
+                            GURL,
+                            std::string /* uuid */)
 IPC_MESSAGE_CONTROL1(BlobHostMsg_RevokePublicURL,
                      GURL)
 
 // Stream messages sent from the renderer to the browser.
 
 // Registers a stream as being built.
-IPC_MESSAGE_CONTROL2(StreamHostMsg_StartBuilding,
-                     GURL /* url */,
-                     std::string /* content_type */)
+//
+// NOTE: This message is synchronous to ensure that the browser is aware of the
+// URL before the URL is passed to another process. This protects against a
+// race condition in which the browser could be asked to load an URL that
+// doesn't yet exist from its perspective.
+//
+IPC_SYNC_MESSAGE_CONTROL2_0(StreamHostMsg_StartBuilding,
+                            GURL /* url */,
+                            std::string /* content_type */)
 
 // Appends data to a stream being built.
 IPC_MESSAGE_CONTROL2(StreamHostMsg_AppendBlobDataItem,
                      GURL /* url */,
                      storage::DataElement)
 
 // Appends data to a stream being built.
 IPC_SYNC_MESSAGE_CONTROL3_0(StreamHostMsg_SyncAppendSharedMemory,
                             GURL /* url */,
                             base::SharedMemoryHandle,
                             uint32_t /* buffer size */)
 
 // Flushes contents buffered in the stream.
 IPC_MESSAGE_CONTROL1(StreamHostMsg_Flush,
                      GURL /* url */)
 
 // Finishes building a stream.
 IPC_MESSAGE_CONTROL1(StreamHostMsg_FinishBuilding,
                      GURL /* url */)
 
 // Aborts building a stream.
 IPC_MESSAGE_CONTROL1(StreamHostMsg_AbortBuilding,
                      GURL /* url */)
 
 // Creates a new stream that's a clone of an existing src stream.
-IPC_MESSAGE_CONTROL2(StreamHostMsg_Clone,
-                     GURL /* url */,
-                     GURL /* src_url */)
+//
+// NOTE: This message is synchronous to ensure that the browser is aware of the
+// URL before the URL is passed to another process. This protects against a
+// race condition in which the browser could be asked to load an URL that
+// doesn't yet exist from its perspective.
+//
+IPC_SYNC_MESSAGE_CONTROL2_0(StreamHostMsg_Clone,
+                            GURL /* url */,
+                            GURL /* src_url */)
 
 // Removes a stream.
 IPC_MESSAGE_CONTROL1(StreamHostMsg_Remove,
                      GURL /* url */)