Add a chrome://flags entry for the popover attribute

This makes it possible for users to opt out of this feature
for a limited time, in the case of site breakage.

(cherry picked from commit 7e294a8)

Bug: 1451587
Bug: 1307772
Change-Id: I5d8a65d9e3785f4d2c1a6b84ca4ad3b260681a93
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4590214
Reviewed-by: Joey Arhar <jarhar@chromium.org>
Commit-Queue: Joey Arhar <jarhar@chromium.org>
Commit-Queue: Mason Freed <masonf@chromium.org>
Auto-Submit: Mason Freed <masonf@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1153565}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4594737
Reviewed-by: Krishna Govind <govind@chromium.org>
Commit-Queue: Krishna Govind <govind@chromium.org>
Owners-Override: Krishna Govind <govind@chromium.org>
Cr-Commit-Position: refs/branch-heads/5790@{#466}
Cr-Branched-From: 1d71a33-refs/heads/main@{#1148114}

chrome/browser/about_flags.cc

@@ -202,6 +202,7 @@
 #include "services/tracing/public/cpp/tracing_features.h"
 #include "storage/browser/quota/quota_features.h"
 #include "third_party/blink/public/common/features.h"
+#include "third_party/blink/public/common/features_generated.h"
 #include "third_party/blink/public/common/forcedark/forcedark_switches.h"
 #include "third_party/blink/public/common/switches.h"
 #include "ui/accessibility/accessibility_features.h"
@@ -5484,6 +5485,9 @@ const FeatureEntry kFeatureEntries[] = {
     {"mutation-events", flag_descriptions::kMutationEventsName,
      flag_descriptions::kMutationEventsDescription, kOsAll,
      FEATURE_VALUE_TYPE(blink::features::kMutationEvents)},
+    {"popover-attribute", flag_descriptions::kHTMLPopoverAttributeName,
+     flag_descriptions::kHTMLPopoverAttributeDescription, kOsAll,
+     FEATURE_VALUE_TYPE(blink::features::kHTMLPopoverAttribute)},
     {"fill-on-account-select", flag_descriptions::kFillOnAccountSelectName,
      flag_descriptions::kFillOnAccountSelectDescription, kOsAll,
      FEATURE_VALUE_TYPE(password_manager::features::kFillOnAccountSelect)},

chrome/browser/flag-metadata.json

@@ -6207,6 +6207,11 @@
     "owners": [ "stkhapugin", "christianxu", "bling-flags@google.com" ],
     "expiry_milestone": 120
   },
+  {
+    "name": "popover-attribute",
+    "owners": [ "masonf" ],
+    "expiry_milestone": 120
+  },
   {
     "name": "power-bookmark-backend",
     "owners": [ "wylieb", "skym" ],

chrome/browser/flag_descriptions.cc

@@ -1594,6 +1594,12 @@ const char kMutationEventsDescription[] =
     "these events can cause breakage on some sites that are still reliant on "
     "these deprecated features.";
 
+const char kHTMLPopoverAttributeName[] = "Enable the popover API";
+const char kHTMLPopoverAttributeDescription[] =
+    "The popover API is a set of features built into the Web to enable the "
+    "construction of popovers. It is accessed primarily via the `popover` "
+    "attribute.";
+
 const char kFillOnAccountSelectName[] = "Fill passwords on account selection";
 const char kFillOnAccountSelectDescription[] =
     "Filling of passwords when an account is explicitly selected by the user "

chrome/browser/flag_descriptions.h

@@ -887,6 +887,9 @@ extern const char kFillingAcrossGroupedSitesDescription[];
 extern const char kMutationEventsName[];
 extern const char kMutationEventsDescription[];
 
+extern const char kHTMLPopoverAttributeName[];
+extern const char kHTMLPopoverAttributeDescription[];
+
 extern const char kFillOnAccountSelectName[];
 extern const char kFillOnAccountSelectDescription[];
 

tools/metrics/histograms/enums.xml

@@ -60357,6 +60357,7 @@ from previous Chrome versions.
   <int value="-1294050129" label="ContentFullscreen:disabled"/>
   <int value="-1293987566" label="OmniboxZeroSuggestionsOnNTPRealbox:disabled"/>
   <int value="-1292766410" label="IntentChipSkipsPicker:disabled"/>
+  <int value="-1292735488" label="HTMLPopoverAttribute:disabled"/>
   <int value="-1292615467"
       label="OmniboxSuggestionTransparencyOptions:disabled"/>
   <int value="-1291963295" label="ComputePressure:disabled"/>
@@ -62724,6 +62725,7 @@ from previous Chrome versions.
   <int value="-40935502" label="ContextualSuggestionsSlimPeekUI:enabled"/>
   <int value="-37966026" label="PermissionPredictions:enabled"/>
   <int value="-37556470" label="FeedBottomSyncBanner:enabled"/>
+  <int value="-36550471" label="HTMLPopoverAttribute:enabled"/>
   <int value="-36503306" label="HomepageLocationPolicy:enabled"/>
   <int value="-36234530" label="PluginVmShowMicrophonePermissions:enabled"/>
   <int value="-36077995" label="SplitCacheByNetworkIsolationKey:disabled"/>