Disable zoom bubble for PDF extension.

extensions/common/features/behavior_feature.h

 // 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.
 
 #ifndef EXTENSIONS_COMMON_FEATURES_BEHAVIOR_FEATURE_H_
 #define EXTENSIONS_COMMON_FEATURES_BEHAVIOR_FEATURE_H_
 
 #include <string>
 
 #include "extensions/common/features/simple_feature.h"
 
 namespace extensions {
 
 // Implementation of the features in _behavior_features.json.
 //
 // For now, this is just constants + a vacuous implementation of SimpleFeature,
 // for consistency with the other Feature types. One day we may add some
 // additional functionality. One day we may also generate the feature names.
 class BehaviorFeature : public SimpleFeature {
  public:
   // Constants corresponding to keys in _behavior_features.json.
   static const char* const kServiceWorker;
   static const char* const kWhitelistedForIncognito;
   static const char* const kDoNotSync;
+  static const char* const kZoomWithoutBubble;
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_FEATURES_BEHAVIOR_FEATURE_H_