Add extensions_browsertests --enable-browser-side-navigation to linux runs

testing/buildbot/chromium.linux.json

Index: testing/buildbot/chromium.linux.json
diff --git a/testing/buildbot/chromium.linux.json b/testing/buildbot/chromium.linux.json
index a28d11b2e81987e65df748a11e33d4cd75b0177b..896093f656a429bf0493304df788c829de2e1deb 100644
--- a/testing/buildbot/chromium.linux.json
+++ b/testing/buildbot/chromium.linux.json
@@ -3043,6 +3043,16 @@
         "test": "extensions_browsertests"
       },
       {
+        "args": [
+          "--enable-browser-side-navigation"
+        ],
+        "name": "browser_side_navigation_extensions_browsertests",
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
+        "test": "extensions_browsertests"
+      },
+      {
         "swarming": {
           "can_use_on_swarming_builders": true
         },
@@ -3641,6 +3651,16 @@
         "test": "extensions_browsertests"
       },
       {
+        "args": [
+          "--enable-browser-side-navigation"
+        ],
+        "name": "browser_side_navigation_extensions_browsertests",
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
+        "test": "extensions_browsertests"
+      },
+      {
         "swarming": {
           "can_use_on_swarming_builders": true
         },