Add deprecation warnings for permission API usage from iframes

third_party/WebKit/public/platform/web_feature.mojom

 // Copyright 2017 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.
 
 module blink.mojom;
 
 // ============ Definition for WebFeature used for UseCounter ===============
 //
 // Do not change assigned numbers of existing items: add new features
 // to the end of the list.
@@ skipping 1568 matching lines @@
   kCSSSelectorWebkitMediaControlsPanel = 2041,
   kCSSSelectorWebkitMediaControlsPlayButton = 2042,
   kCSSSelectorWebkitMediaControlsCurrentTimeDisplay = 2043,
   kCSSSelectorWebkitMediaControlsTimeRemainingDisplay = 2044,
   kCSSSelectorWebkitMediaControlsTimeline = 2045,
   kCSSSelectorWebkitMediaControlsTimelineContainer = 2046,
   kCSSSelectorWebkitMediaControlsMuteButton = 2047,
   kCSSSelectorWebkitMediaControlsVolumeSlider = 2048,
   kCSSSelectorWebkitMediaControlsFullscreenButton = 2049,
   kCSSSelectorWebkitMediaControlsToggleClosedCaptionsButton = 2050,
+  kEncryptedMediaDisabledCrossOriginIframe = 2051,

[ddorwin, 2017/07/05 20:29:20]

"Disabled" here seems misleading. 
...CrossOriginIframeWithoutpermission?

[raymes, 2017/07/06 03:48:04]

Hmm, that could imply user permission was denied though. I made it really
verbose but clear:
kEncryptedMediaDisabledInCrossOriginIframeDueToFeaturePolicy

[ddorwin, 2017/07/06 23:28:21]

I was trying to find language that indicated the condition (no explicit
allowance for the iframe) without indicating what happened, since that will
change in a future release. In this case, "Disabled" could imply the future
behavior. I guess that's more future-proof if we intend to keep the stat for
reporting when it is really disallowed (no longer a deprecation counter but a
normal counter). I'm not sure how useful that will be, though.

[raymes, 2017/07/10 23:19:13]

Ah I understand. Thanks for explaining. It's hard to phrase exactly because it
is still "disallowed by feature policy" but we're just not enforcing the feature
policy right now.

I've gone with DisallowedByFeaturePolicyInCrossOriginIframe which is hopefully
good enough :)

+  kGeolocationDisabledCrossOriginIframe = 2052,
+  kGetUserMediaMicDisabledCrossOriginIframe = 2053,
+  kGetUserMediaCameraDisabledCrossOriginIframe = 2054,
+  kRequestMIDIAccessDisabledCrossOriginIframe = 2055,
 
   // Add new features immediately above this line. Don't change assigned
   // numbers of any item, and don't reuse removed slots.
   // Also, run update_use_counter_feature_enum.py in
   // chromium/src/tools/metrics/histograms/ to update the UMA mapping.
   kNumberOfFeatures,  // This enum value must be last.
 };