[FlexNG] Field trial config

This makes browser_tests and unit_tests use FlexNG. It's required before
launching a stable experiment.

Bug: 845235, 1062484
Change-Id: If5e9672bcf11c62d8ff92f1939608d8ab969682b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2205975Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Reviewed-by: Moe Ahmadi <mahmadi@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: David Grogan <dgrogan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#771070}

chrome/browser/ui/search/local_ntp_doodle_browsertest.cc

@@ -1393,7 +1393,10 @@ IN_PROC_BROWSER_TEST_F(LocalNTPDoodleTest, ShouldNotMoveFakeboxForIframeSizes) {
   }
 }
 
-IN_PROC_BROWSER_TEST_F(LocalNTPDoodleTest, ShouldMoveFakeboxWhenIframeResized) {
+// Fails on gLinux with legacy flexbox. Fails locally and on bots with FlexNG.
+// https://crbug.com/1062484
+IN_PROC_BROWSER_TEST_F(LocalNTPDoodleTest,
+                       DISABLED_ShouldMoveFakeboxWhenIframeResized) {
   EncodedLogo cached_logo;
   cached_logo.encoded_image = MakeRefPtr(std::string());
   cached_logo.metadata.mime_type = "image/png";

testing/variations/fieldtrial_testing_config.json

@@ -2330,6 +2330,26 @@
             ]
         }
     ],
+    "FlexNG": [
+        {
+            "platforms": [
+                "android",
+                "android_webview",
+                "chromeos",
+                "linux",
+                "mac",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled_20200406",
+                    "enable_features": [
+                        "FlexNG"
+                    ]
+                }
+            ]
+        }
+    ],
     "FontPreloadingDelaysRendering": [
         {
             "platforms": [