Expose the Site Engagement Service to Java.

This CL adds a Java-side interface to the Site Engagement Service, as
well as a basic integration test for the interface. This allows Java
code (particularly tests) to programatically adjust and retrieve the
score.

BUG=671100

Review-Url: https://codereview.chromium.org/2553013002
Cr-Commit-Position: refs/heads/master@{#437825}
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index a166fed8..f59ef26 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -3255,6 +3255,8 @@
       "dom_distiller/tab_utils_android.h",
       "download/download_request_infobar_delegate_android.cc",
       "download/download_request_infobar_delegate_android.h",
+      "engagement/site_engagement_service_android.cc",
+      "engagement/site_engagement_service_android.h",
       "geolocation/geolocation_infobar_delegate_android.cc",
       "geolocation/geolocation_infobar_delegate_android.h",
       "history/android/android_history_provider_service.cc",
@@ -3907,6 +3909,7 @@
       "../android/java/src/org/chromium/chrome/browser/download/DownloadItem.java",
       "../android/java/src/org/chromium/chrome/browser/download/DownloadManagerService.java",
       "../android/java/src/org/chromium/chrome/browser/download/ui/ThumbnailProviderImpl.java",
+      "../android/java/src/org/chromium/chrome/browser/engagement/SiteEngagementService.java",
       "../android/java/src/org/chromium/chrome/browser/favicon/FaviconHelper.java",
       "../android/java/src/org/chromium/chrome/browser/favicon/LargeIconBridge.java",
       "../android/java/src/org/chromium/chrome/browser/feedback/ConnectivityChecker.java",