nacl: Fix a bunch of compiler warnings

ipc/ipc_channel_nacl.cc

Index: ipc/ipc_channel_nacl.cc
diff --git a/ipc/ipc_channel_nacl.cc b/ipc/ipc_channel_nacl.cc
index 4231dd8bca8387ff73e048bee300c206cc318bf5..e7f11db4ed60690006ca461733e2f8edb52cd3ad 100644
--- a/ipc/ipc_channel_nacl.cc
+++ b/ipc/ipc_channel_nacl.cc
@@ -261,7 +261,7 @@ bool Channel::ChannelImpl::ProcessOutgoingMessages() {
     output_queue_.pop_front();
 
     int fds[FileDescriptorSet::kMaxDescriptorsPerMessage];
-    const int num_fds = msg->file_descriptor_set()->size();
+    const size_t num_fds = msg->file_descriptor_set()->size();
     DCHECK(num_fds <= FileDescriptorSet::kMaxDescriptorsPerMessage);
     msg->file_descriptor_set()->GetDescriptors(fds);
 
@@ -302,7 +302,7 @@ Channel::ChannelImpl::ReadState Channel::ChannelImpl::ReadData(
     return READ_PENDING;
   while (!read_queue_.empty() && *bytes_read < buffer_len) {
     linked_ptr<std::vector<char> > vec(read_queue_.front());
-    int bytes_to_read = buffer_len - *bytes_read;
+    size_t bytes_to_read = buffer_len - *bytes_read;
     if (vec->size() <= bytes_to_read) {
       // We can read and discard the entire vector.
       std::copy(vec->begin(), vec->end(), buffer + *bytes_read);