[Offline Pages] Add basic evaluation tests and related changes.

This change includes some changes for the basic evaluation tests.
1. Evaluation Java test file.
2. Evaluation scheduler which would only be used in testing and will
start the processing of requests immediately. This will be injected in
request coordinator factory as a testing class.
3. Build files related.

BUG=646947

Review-Url: https://codereview.chromium.org/2432593002
Cr-Commit-Position: refs/heads/master@{#427913}
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index 7e5c46b..85d7dfd 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -3372,6 +3372,8 @@
     # Used for testing only, should not be shipped to end users.
     if (!is_official_build) {
       sources += [
+        "android/offline_pages/evaluation/evaluation_test_scheduler.cc",
+        "android/offline_pages/evaluation/evaluation_test_scheduler.h",
         "android/offline_pages/evaluation/offline_page_evaluation_bridge.cc",
         "android/offline_pages/evaluation/offline_page_evaluation_bridge.h",
       ]