[Tentaive patch for discussion] Add Purge+Suspend metrics as UMA.

content/public/common/content_features.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 "build/build_config.h"
 #include "content/public/common/content_features.h"
 
 namespace features {
 
 // All features in alphabetical order.
@@ skipping 106 matching lines @@
 
 // Pointer events support.
 const base::Feature kPointerEvents{"PointerEvent",
                                    base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Whether pointer event capturing follow v1 spec instead of v2 proposal.
 // See https://rawgit.com/w3c/pointerevents/reduce-hit-tests/index.html.
 const base::Feature kPointerEventV1SpecCapturing{
     "PointerEventV1SpecCapturing", base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Purge and suspend for background renderers.
+const base::Feature kPurgeAndSuspend{"PurgeAndSuspend",
+                                     base::FEATURE_DISABLED_BY_DEFAULT};
+
 // RAF aligned input events support.
 const base::Feature kRafAlignedInputEvents{"RafAlignedInput",
                                            base::FEATURE_DISABLED_BY_DEFAULT};
 
 // If Pepper 3D Image Chromium is allowed, this feature controls whether it is
 // enabled.
 const base::Feature kPepper3DImageChromium{"Pepper3DImageChromium",
                                            base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Throttle Blink's rendering pipeline based on frame visibility.
@@ skipping 67 matching lines @@
 #endif
 
 #if defined(OS_WIN)
 // Emergency "off switch" for new Windows sandbox security mitigation,
 // sandbox::MITIGATION_EXTENSION_POINT_DISABLE.
 const base::Feature kWinSboxDisableExtensionPoints{
     "WinSboxDisableExtensionPoint", base::FEATURE_ENABLED_BY_DEFAULT};
 #endif
 
 }  // namespace features