Convert IdentityServicesProvider.java to new JNI invocation convention

As found in //base/android/jni_generator/README.md, the convention of
marking method with "native" is deprecated and instead the new
convention is to mark an interface with @NativeMethods. This Converts
IdentityServicesProvider.java to the new JNI invocation convention.

Bug: 934688
Change-Id: Id080c86546ce09457f34c21a8ddf9870625b60a9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1738368
Commit-Queue: Pâris Meuleman <pmeuleman@chromium.org>
Reviewed-by: Boris Sazonov <bsazonov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#685504}

chrome/android/java/src/org/chromium/chrome/browser/signin/IdentityServicesProvider.java

@@ -5,6 +5,7 @@
 package org.chromium.chrome.browser.signin;
 
 import org.chromium.base.ThreadUtils;
+import org.chromium.base.annotations.NativeMethods;
 import org.chromium.chrome.browser.profiles.Profile;
 import org.chromium.components.signin.AccountTrackerService;
 import org.chromium.components.signin.OAuth2TokenService;
@@ -18,7 +19,8 @@ public final class IdentityServicesProvider {
     /** Getter for {@link IdentityManager} instance. */
     public static IdentityManager getIdentityManager() {
         ThreadUtils.assertOnUiThread();
-        IdentityManager result = nativeGetIdentityManager(Profile.getLastUsedProfile());
+        IdentityManager result =
+                IdentityServicesProviderJni.get().getIdentityManager(Profile.getLastUsedProfile());
         assert result != null;
         return result;
     }
@@ -26,27 +28,33 @@ public final class IdentityServicesProvider {
     /** Getter for {@link AccountTrackerService} instance. */
     public static AccountTrackerService getAccountTrackerService() {
         ThreadUtils.assertOnUiThread();
-        AccountTrackerService result = nativeGetAccountTrackerService(Profile.getLastUsedProfile());
+        AccountTrackerService result = IdentityServicesProviderJni.get().getAccountTrackerService(
+                Profile.getLastUsedProfile());
         assert result != null;
         return result;
     }
 
     public static OAuth2TokenService getOAuth2TokenService() {
         ThreadUtils.assertOnUiThread();
-        OAuth2TokenService result = nativeGetOAuth2TokenService(Profile.getLastUsedProfile());
+        OAuth2TokenService result = IdentityServicesProviderJni.get().getOAuth2TokenService(
+                Profile.getLastUsedProfile());
         assert result != null;
         return result;
     }
 
     public static SigninManager getSigninManager() {
         ThreadUtils.assertOnUiThread();
-        SigninManager result = nativeGetSigninManager(Profile.getLastUsedProfile());
+        SigninManager result =
+                IdentityServicesProviderJni.get().getSigninManager(Profile.getLastUsedProfile());
         assert result != null;
         return result;
     }
 
-    private static native IdentityManager nativeGetIdentityManager(Profile profile);
-    private static native AccountTrackerService nativeGetAccountTrackerService(Profile profile);
-    private static native OAuth2TokenService nativeGetOAuth2TokenService(Profile profile);
-    private static native SigninManager nativeGetSigninManager(Profile profile);
+    @NativeMethods
+    interface Natives {
+        public IdentityManager getIdentityManager(Profile profile);
+        public AccountTrackerService getAccountTrackerService(Profile profile);
+        public OAuth2TokenService getOAuth2TokenService(Profile profile);
+        public SigninManager getSigninManager(Profile profile);
+    }
 }