Deprecate MessageLoop::Type

It is currently just an alias to MessagePump::Type. This patch changes
a bunch of references to use MessagePump::Type as MessageLoop will eventually
disappear.

Also rename base::Thread::Options::message_loop_type to message_pump_type
It is weird to see things like

message_loop_type = MessagePump::Type::UI

Also change some other instances that I happened to see in the form
loop_type = MessagePump::Type::UI
to
pump_type = MessagePump::Type::UI

This is a mechanical change that will be reviewed according to
https://chromium.googlesource.com/chromium/src/+/master/docs/code_reviews.md#mechanical-changes

BUG=891670
[email protected]

Change-Id: Ib41ccc6547b8c9fa0bdba5d23c4767ae03f2a97d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1718331
Commit-Queue: Carlos Caballero <[email protected]>
Reviewed-by: Gabriel Charette <[email protected]>
Cr-Commit-Position: refs/heads/master@{#682254}
diff --git a/net/test/tcp_socket_proxy_unittest.cc b/net/test/tcp_socket_proxy_unittest.cc
index 8a33129..54bde532 100644
--- a/net/test/tcp_socket_proxy_unittest.cc
+++ b/net/test/tcp_socket_proxy_unittest.cc
@@ -4,7 +4,7 @@
 
 #include "net/test/tcp_socket_proxy.h"
 
-#include "base/message_loop/message_loop.h"
+#include "base/message_loop/message_pump_type.h"
 #include "base/threading/thread.h"
 #include "build/build_config.h"
 #include "net/base/io_buffer.h"
@@ -25,7 +25,7 @@
  public:
   TcpSocketProxyTest() : io_thread_("TcpSocketProxyTest IO Thread") {
     EXPECT_TRUE(io_thread_.StartWithOptions(
-        base::Thread::Options(base::MessageLoop::TYPE_IO, 0)));
+        base::Thread::Options(base::MessagePumpType::IO, 0)));
 
     listen_socket_ =
         std::make_unique<TCPServerSocket>(nullptr, net::NetLogSource());