Handle pending WebAuthn requests on Android properly

Subsequent requests while a request is on-going get canceled
with a PENDING_REQUEST error on both desktop and Android, except
that on Android the callback for the legitimate request was getting
overriden by the subsequent request, leading to a crash.

Bug: 958542
Change-Id: Ie6d5b096abddb66aa4933a5331c689357791c3f3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1624606Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Commit-Queue: Kim Paulhamus <kpaulhamus@chromium.org>
Cr-Commit-Position: refs/heads/master@{#662638}

chrome/android/java/src/org/chromium/chrome/browser/webauth/AuthenticatorImpl.java

@@ -55,6 +55,11 @@ public class AuthenticatorImpl implements Authenticator, HandlerResponseCallback
     @Override
     public void makeCredential(
             PublicKeyCredentialCreationOptions options, MakeCredentialResponse callback) {
+        if (mIsOperationPending) {
+            callback.call(AuthenticatorStatus.PENDING_REQUEST, null);
+            return;
+        }
+
         mMakeCredentialCallback = callback;
         Context context = ChromeActivity.fromWebContents(mWebContents);
         if (PackageUtils.getPackageVersion(context, GMSCORE_PACKAGE_NAME) < GMSCORE_MIN_VERSION) {
@@ -62,11 +67,6 @@ public class AuthenticatorImpl implements Authenticator, HandlerResponseCallback
             return;
         }
 
-        if (mIsOperationPending) {
-            onError(AuthenticatorStatus.PENDING_REQUEST);
-            return;
-        }
-
         mIsOperationPending = true;
         Fido2ApiHandler.getInstance().makeCredential(options, mRenderFrameHost, this);
     }
@@ -74,6 +74,11 @@ public class AuthenticatorImpl implements Authenticator, HandlerResponseCallback
     @Override
     public void getAssertion(
             PublicKeyCredentialRequestOptions options, GetAssertionResponse callback) {
+        if (mIsOperationPending) {
+            callback.call(AuthenticatorStatus.PENDING_REQUEST, null);
+            return;
+        }
+
         mGetAssertionCallback = callback;
         Context context = ChromeActivity.fromWebContents(mWebContents);
         if (PackageUtils.getPackageVersion(context, GMSCORE_PACKAGE_NAME) < GMSCORE_MIN_VERSION) {
@@ -81,11 +86,6 @@ public class AuthenticatorImpl implements Authenticator, HandlerResponseCallback
             return;
         }
 
-        if (mIsOperationPending) {
-            onError(AuthenticatorStatus.PENDING_REQUEST);
-            return;
-        }
-
         mIsOperationPending = true;
         Fido2ApiHandler.getInstance().getAssertion(options, mRenderFrameHost, this);
     }