Add Apps.AppListSearchQueryLength UMA histogram.

ui/app_list/app_list_constants.h

 // Copyright (c) 2012 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 UI_APP_LIST_APP_LIST_CONSTANTS_H_
 #define UI_APP_LIST_APP_LIST_CONSTANTS_H_
 
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/app_list/app_list_export.h"
 #include "ui/base/resource/resource_bundle.h"
@@ skipping 65 matching lines @@
 APP_LIST_EXPORT extern const int kExperimentalSearchBoxPadding;
 
 APP_LIST_EXPORT extern size_t kMaxFolderItems;
 APP_LIST_EXPORT extern const size_t kNumFolderTopItems;
 APP_LIST_EXPORT extern const size_t kMaxFolderNameChars;
 
 APP_LIST_EXPORT extern const ui::ResourceBundle::FontStyle kItemTextFontStyle;
 
 APP_LIST_EXPORT extern const char kPageOpenedHistogram[];
 APP_LIST_EXPORT extern const char kSearchResultOpenDisplayTypeHistogram[];
+APP_LIST_EXPORT extern const char kSearchQueryLength[];
 
 #if defined(OS_LINUX)
 // The WM_CLASS name for the app launcher window on Linux.
 APP_LIST_EXPORT extern const char kAppListWMClass[];
 #endif
 
 // Returns the shadow values for a view at |z_height|.
 gfx::ShadowValue APP_LIST_EXPORT GetShadowForZHeight(int z_height);
 
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_APP_LIST_CONSTANTS_H_