Show a better error message for captureVisibleTab than just "internal error".

chrome/browser/extensions/api/tabs/tabs_constants.cc

 // 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.
 
 #include "chrome/browser/extensions/api/tabs/tabs_constants.h"
 
 namespace extensions {
 namespace tabs_constants {
 
 const char kActiveKey[] = "active";
@@ skipping 73 matching lines @@
 const char kTabStripNotEditableError[] =
     "Tabs cannot be edited right now (user may be dragging a tab).";
 const char kNoSelectedTabError[] = "No selected tab";
 const char kNoHighlightedTabError[] = "No highlighted tab";
 const char kIncognitoModeIsDisabled[] = "Incognito mode is disabled.";
 const char kIncognitoModeIsForced[] = "Incognito mode is forced. "
     "Cannot open normal windows.";
 const char kURLsNotAllowedInIncognitoError[] = "Cannot open URL \"*\" "
     "in an incognito window.";
 const char kInvalidUrlError[] = "Invalid url: \"*\".";
-const char kInternalVisibleTabCaptureError[] =
-    "Internal error while trying to capture visible region of the current tab";
 const char kNotImplementedError[] = "This call is not yet implemented";
 const char kSupportedInWindowsOnlyError[] = "Supported in Windows only";
 const char kInvalidWindowTypeError[] = "Invalid value for type";
 const char kInvalidWindowStateError[] = "Invalid value for state";
 const char kScreenshotsDisabled[] = "Taking screenshots has been disabled";
 
 const char kCannotDetermineLanguageOfUnloadedTab[] =
     "Cannot determine language: tab not loaded";
 
 }  // namespace tabs_constants
 }  // namespace extensions