Use the tonic namespace for tonic + resulting build fixes

tonic/dart_dependency_catcher.cc

 // Copyright 2015 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_dependency_catcher.h"
 
 #include "tonic/dart_library_loader.h"
 
-namespace blink {
+namespace tonic {
 
 DartDependencyCatcher::DartDependencyCatcher(DartLibraryLoader& loader)
     : loader_(loader) {
   loader_.set_dependency_catcher(this);
 }
 
 DartDependencyCatcher::~DartDependencyCatcher() {
   loader_.set_dependency_catcher(nullptr);
 }
 
 void DartDependencyCatcher::AddDependency(DartDependency* dependency) {
   dependencies_.insert(dependency);
 }
 
-}  // namespace blink
+}  // namespace tonic