Make chrome://flags control whether the WebAPK feature is on

chrome/common/chrome_switches.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.
 
 // Defines the shared command-line switches used by code in the Chrome
 // directory that don't have anywhere more specific to go.
 
 #ifndef CHROME_COMMON_CHROME_SWITCHES_H_
 #define CHROME_COMMON_CHROME_SWITCHES_H_
 
@@ skipping 266 matching lines @@
 extern const char kDisableAppLink[];
 extern const char kDisableContextualSearch[];
 extern const char kDisableVrShell[];
 extern const char kEnableAccessibilityTabSwitcher[];
 extern const char kEnableAppLink[];
 extern const char kEnableContextualSearch[];
 extern const char kEnableContextualSearchContextualCardsBarIntegration[];
 extern const char kEnableHostedMode[];
 extern const char kEnableHungRendererInfoBar[];
 extern const char kEnableVrShell[];
-extern const char kEnableWebApk[];
 extern const char kForceShowUpdateMenuBadge[];
 extern const char kForceShowUpdateMenuItem[];
 extern const char kForceShowUpdateMenuItemCustomSummary[];
 extern const char kForceShowUpdateMenuItemNewFeaturesSummary[];
 extern const char kForceShowUpdateMenuItemSummary[];
 extern const char kMarketUrlForTesting[];
 extern const char kNtpSwitchToExistingTab[];
 extern const char kProgressBarAnimation[];
 extern const char kTabManagementExperimentTypeDisabled[];
 extern const char kTabManagementExperimentTypeElderberry[];
@@ skipping 91 matching lines @@
 #if defined(OS_WIN)
 bool GDITextPrintingEnabled();
 #endif
 
 // DON'T ADD RANDOM STUFF HERE. Put it in the main section above in
 // alphabetical order, or in one of the ifdefs (also in order in each section).
 
 }  // namespace switches
 
 #endif  // CHROME_COMMON_CHROME_SWITCHES_H_