Use the tonic namespace for tonic + resulting build fixes

tonic/dart_value.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_value.h"
 
-namespace blink {
+namespace tonic {
 
 DartValue::DartValue() {
 }
 
 DartValue::DartValue(DartState* dart_state, Dart_Handle value)
     : dart_value_(dart_state, value) {
 }
 
 DartValue::~DartValue() {
 }
 
 bool DartValue::Equals(DartValue* other) const {
   DCHECK(other);
   if (is_empty())
     return other->is_empty();
   if (other->is_empty())
     return false;
   return Dart_IdentityEquals(dart_value(), other->dart_value());
 }
 
 void DartValue::Clear() {
   dart_value_.Clear();
 }
 
-}  // namespace blink
+}  // namespace tonic