Rewrite clipboard write IPC handling to be easier to understand.

ui/base/test/test_clipboard.cc

 // Copyright 2014 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.
 
 #include "ui/base/test/test_clipboard.h"
 
 #include <stddef.h>
 #include "base/numerics/safe_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 
 namespace ui {
 
 TestClipboard::TestClipboard()
     : default_store_type_(CLIPBOARD_TYPE_COPY_PASTE) {
 }
 
 TestClipboard::~TestClipboard() {
 }
 
-void TestClipboard::UseForCurrentThread() {
+Clipboard* TestClipboard::CreateForCurrentThread() {
   base::AutoLock lock(Clipboard::clipboard_map_lock_.Get());
+  Clipboard* clipboard = new TestClipboard;
   Clipboard::clipboard_map_.Get()[base::PlatformThread::CurrentId()] =
-      new TestClipboard;
+      clipboard;
+  return clipboard;
 }
 
 uint64 TestClipboard::GetSequenceNumber(ClipboardType type) const {
   return GetStore(type).sequence_number;
 }
 
 bool TestClipboard::IsFormatAvailable(const FormatType& format,
                                       ClipboardType type) const {
   const DataStore& store = GetStore(type);
   return store.data.find(format) != store.data.end();
@@ skipping 158 matching lines @@
 
 const TestClipboard::DataStore& TestClipboard::GetDefaultStore() const {
   return GetStore(default_store_type_);
 }
 
 TestClipboard::DataStore& TestClipboard::GetDefaultStore() {
   return GetStore(default_store_type_);
 }
 
 }  // namespace ui