blink: add a use counter for WebAuthn isUVPAA() invocations

This adds a use counter for calls to
PublicKeyCredential.isUserVerifyingPlatformAuthenticatorAvailable(). The
counter's name is prefixed with `kCredentialManager` for consistency
with other WebAuthn related metrics.

Fixed: 1018318
Change-Id: I2ba0e96a37405b7774259c09eb34c534ee43f640
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1880319
Commit-Queue: Martin Kreichgauer <martinkr@google.com>
Auto-Submit: Martin Kreichgauer <martinkr@google.com>
Reviewed-by: Adam Langley <agl@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710056}

third_party/blink/public/mojom/web_feature/web_feature.mojom

@@ -2455,6 +2455,7 @@ enum WebFeature {
   kDOMWindowOpenPositioningFeatures = 3071,
   kMouseEventScreenX = 3072,
   kMouseEventScreenY = 3073,
+  kCredentialManagerIsUserVerifyingPlatformAuthenticatorAvailable = 3074,
 
   // Add new features immediately above this line. Don't change assigned
   // numbers of any item, and don't reuse removed slots.

third_party/blink/renderer/modules/credentialmanager/public_key_credential.cc

@@ -7,9 +7,11 @@
 #include "third_party/blink/renderer/bindings/core/v8/script_promise.h"
 #include "third_party/blink/renderer/bindings/core/v8/script_promise_resolver.h"
 #include "third_party/blink/renderer/core/dom/dom_exception.h"
+#include "third_party/blink/renderer/core/frame/web_feature.h"
 #include "third_party/blink/renderer/modules/credentialmanager/credential_manager_proxy.h"
 #include "third_party/blink/renderer/modules/credentialmanager/scoped_promise_resolver.h"
 #include "third_party/blink/renderer/platform/bindings/script_state.h"
+#include "third_party/blink/renderer/platform/instrumentation/use_counter.h"
 #include "third_party/blink/renderer/platform/wtf/functional.h"
 
 namespace blink {
@@ -49,6 +51,11 @@ PublicKeyCredential::isUserVerifyingPlatformAuthenticatorAvailable(
     return promise;
   }
 
+  UseCounter::Count(
+      resolver->GetExecutionContext(),
+      WebFeature::
+          kCredentialManagerIsUserVerifyingPlatformAuthenticatorAvailable);
+
   auto* authenticator =
       CredentialManagerProxy::From(script_state)->Authenticator();
   authenticator->IsUserVerifyingPlatformAuthenticatorAvailable(WTF::Bind(

tools/metrics/histograms/enums.xml

@@ -25196,6 +25196,8 @@ Called by update_net_error_codes.py.-->
   <int value="3071" label="DOMWindowOpenPositioningFeatures"/>
   <int value="3072" label="MouseEventScreenX"/>
   <int value="3073" label="MouseEventScreenY"/>
+  <int value="3074"
+      label="CredentialManagerIsUserVerifyingPlatformAuthenticatorAvailable"/>
 </enum>
 
 <enum name="FeaturePolicyAllowlistType">