Revert of Removing the ChildProcessHostMsg_SyncAllocateSharedMemory IPC message.

content/common/child_process_host_impl.cc

Index: content/common/child_process_host_impl.cc
diff --git a/content/common/child_process_host_impl.cc b/content/common/child_process_host_impl.cc
index 59325c330ddfeece1e2a14bdcd3a87c708736a7a..71a34fcc6d9e244060725270f20ecda6b6fa252a 100644
--- a/content/common/child_process_host_impl.cc
+++ b/content/common/child_process_host_impl.cc
@@ -185,6 +185,18 @@
   return channel_->Send(message);
 }
 
+void ChildProcessHostImpl::AllocateSharedMemory(
+      size_t buffer_size, base::ProcessHandle child_process_handle,
+      base::SharedMemoryHandle* shared_memory_handle) {
+  base::SharedMemory shared_buf;
+  if (!shared_buf.CreateAnonymous(buffer_size)) {
+    *shared_memory_handle = base::SharedMemory::NULLHandle();
+    NOTREACHED() << "Cannot create shared memory buffer";
+    return;
+  }
+  shared_buf.GiveToProcess(child_process_handle, shared_memory_handle);
+}
+
 int ChildProcessHostImpl::GenerateChildProcessUniqueId() {
   // This function must be threadsafe.
   //
@@ -243,9 +255,12 @@
     IPC_BEGIN_MESSAGE_MAP(ChildProcessHostImpl, msg)
       IPC_MESSAGE_HANDLER(ChildProcessHostMsg_ShutdownRequest,
                           OnShutdownRequest)
-      // NB: The SyncAllocateGpuMemoryBuffer and DeletedGpuMemoryBuffer IPCs are
-      // handled here for non-renderer child processes. For renderer processes,
-      // they are handled in RenderMessageFilter.
+      // NB: The SyncAllocateSharedMemory, SyncAllocateGpuMemoryBuffer, and
+      // DeletedGpuMemoryBuffer IPCs are handled here for non-renderer child
+      // processes. For renderer processes, they are handled in
+      // RenderMessageFilter.
+      IPC_MESSAGE_HANDLER(ChildProcessHostMsg_SyncAllocateSharedMemory,
+                          OnAllocateSharedMemory)
       IPC_MESSAGE_HANDLER(ChildProcessHostMsg_SyncAllocateGpuMemoryBuffer,
                           OnAllocateGpuMemoryBuffer)
       IPC_MESSAGE_HANDLER(ChildProcessHostMsg_DeletedGpuMemoryBuffer,
@@ -290,6 +305,12 @@
 
 void ChildProcessHostImpl::OnBadMessageReceived(const IPC::Message& message) {
   delegate_->OnBadMessageReceived(message);
+}
+
+void ChildProcessHostImpl::OnAllocateSharedMemory(
+    uint32_t buffer_size,
+    base::SharedMemoryHandle* handle) {
+  AllocateSharedMemory(buffer_size, peer_process_.Handle(), handle);
 }
 
 void ChildProcessHostImpl::OnShutdownRequest() {