Reland of Finch code for OfflinePagesSharing

Ensures that test bots cover OfflinePagesSharing flag scenarios.

This was reverted because of a flaky unit test.
The test has been disabled, and a new bug has been filed to investigate.

Bug: 758733
Change-Id: I7043ffe7d520869f79abdc6c80d6bcdbe8029651
Reviewed-on: https://chromium-review.googlesource.com/1043349Reviewed-by: David Trainor <dtrainor@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Jian Li <jianli@chromium.org>
Commit-Queue: Peter Williamson <petewil@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#557636}
Reviewed-on: https://chromium-review.googlesource.com/1056221Reviewed-by: Jesse Doherty <jwd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558455}

chrome/android/javatests/src/org/chromium/chrome/browser/download/DownloadActivityTest.java

@@ -47,6 +47,7 @@ import org.chromium.chrome.browser.widget.ListMenuButton.Item;
 import org.chromium.chrome.browser.widget.selection.SelectionDelegate.SelectionObserver;
 import org.chromium.chrome.test.ChromeJUnit4ClassRunner;
 import org.chromium.chrome.test.util.browser.Features;
+import org.chromium.chrome.test.util.browser.Features.DisableFeatures;
 import org.chromium.chrome.test.util.browser.Features.EnableFeatures;
 import org.chromium.components.offline_items_collection.OfflineItem;
 import org.chromium.content.browser.test.util.Criteria;
@@ -512,6 +513,7 @@ public class DownloadActivityTest {
 
     @Test
     @MediumTest
+    @DisableFeatures("OfflinePagesSharing")
     public void testShareFiles() throws Exception {
         // Adapter positions:
         // 0 = space display

chrome/android/javatests/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridgeTest.java

@@ -20,6 +20,7 @@ import org.chromium.base.ApiCompatibilityUtils;
 import org.chromium.base.Callback;
 import org.chromium.base.ThreadUtils;
 import org.chromium.base.test.util.CommandLineFlags;
+import org.chromium.base.test.util.DisabledTest;
 import org.chromium.base.test.util.RetryOnFailure;
 import org.chromium.chrome.browser.ChromeActivity;
 import org.chromium.chrome.browser.ChromeSwitches;
@@ -403,6 +404,7 @@ public class OfflinePageBridgeTest {
 
     @Test
     @SmallTest
+    @DisabledTest(message = "crbug.com/842801")
     public void testSavePageNoOrigin() throws Exception {
         mActivityTestRule.loadUrl(mTestPage);
         savePage(SavePageResult.SUCCESS, mTestPage);

testing/variations/fieldtrial_testing_config.json

@@ -2287,6 +2287,21 @@
             ]
         }
     ],
+    "OfflinePagesSharing": [
+        {
+            "platforms": [
+                "android"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "OfflinePagesSharing"
+                    ]
+                }
+            ]
+        }
+    ],
     "OmniboxBundledExperimentV1": [
         {
             "platforms": [