[Extensions Bindings] Add a fieldtrial testing config entry for native bindings

We're getting ready to roll extension bindings out to beta, so add a
fieldtrial testing config entry for the experiment to have it run by
default on the bots.

Bug: 763564

Change-Id: Ibdf83e16cbc10e4c62e2304cf14cd7c24377bc31
Reviewed-on: https://chromium-review.googlesource.com/1108192Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Istiaque Ahmed <lazyboy@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569277}

chrome/browser/extensions/error_console/error_console_browsertest.cc

@@ -492,8 +492,7 @@ IN_PROC_BROWSER_TEST_F(ErrorConsoleBrowserTest, BadAPIArgumentsRuntimeError) {
     message =
         "Uncaught TypeError: Error in invocation of "
         "tabs.get(integer tabId, function callback): "
-        "Error at parameter 'tabId': Invalid type: "
-        "expected integer, found string.";
+        "No matching signature.";
   } else {
     // API calls are checked in schemaUtils.js with JS bindings.
     source = "extensions::" + std::string(kSchemaUtils);

testing/variations/fieldtrial_testing_config.json

@@ -2345,6 +2345,24 @@
             ]
         }
     ],
+    "NativeCrxBindings": [
+        {
+            "platforms": [
+                "chromeos",
+                "linux",
+                "mac",
+                "win"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "NativeCrxBindings"
+                    ]
+                }
+            ]
+        }
+    ],
     "NetworkQualityEstimator": [
         {
             "platforms": [