Revert of Removing the ChildProcessHostMsg_SyncAllocateSharedMemory IPC message.

content/common/child_process_messages.h

Index: content/common/child_process_messages.h
diff --git a/content/common/child_process_messages.h b/content/common/child_process_messages.h
index fefc94fcfc6ac8ead7f12db09867466fcd785370..c74214a181ac64ef60d1d4b30666f8cc51badce9 100644
--- a/content/common/child_process_messages.h
+++ b/content/common/child_process_messages.h
@@ -176,6 +176,12 @@
 
 // Asks the browser to create a block of shared memory for the child process to
 // fill in and pass back to the browser.
+IPC_SYNC_MESSAGE_CONTROL1_1(ChildProcessHostMsg_SyncAllocateSharedMemory,
+                            uint32_t /* buffer size */,
+                            base::SharedMemoryHandle)
+
+// Asks the browser to create a block of shared memory for the child process to
+// fill in and pass back to the browser.
 IPC_SYNC_MESSAGE_CONTROL2_1(ChildProcessHostMsg_SyncAllocateSharedBitmap,
                             uint32_t /* buffer size */,
                             cc::SharedBitmapId,