Use the tonic namespace for tonic + resulting build fixes

tonic/dart_string_cache.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 "tonic/dart_string_cache.h"
 
 #include "tonic/dart_state.h"
 #include "tonic/dart_string.h"
 
-namespace blink {
+namespace tonic {
 
 DartStringCache::DartStringCache() : last_dart_string_(nullptr) {
 }
 
 DartStringCache::~DartStringCache() {
 }
 
 Dart_WeakPersistentHandle DartStringCache::GetSlow(StringImpl* string_impl,
                                                    bool auto_scope) {
   if (Dart_WeakPersistentHandle string = cache_.get(string_impl)) {
@@ skipping 35 matching lines @@
   ASSERT_UNUSED(cached_handle, handle == cached_handle);
 
   if (cache.last_dart_string_ == handle) {
     cache.last_dart_string_ = nullptr;
     cache.last_string_impl_ = nullptr;
   }
 
   string_impl->deref();
 }
 
-}  // namespace blink
+}  // namespace tonic