Adding field trial for omnibox spare renderer

Bug: 1114903
Change-Id: I14e3ae3cc1842686fd4b92e428729ef7f59cdbaf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2350745Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Ryan Sturm <ryansturm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797103}

testing/variations/fieldtrial_testing_config.json

@@ -5030,6 +5030,21 @@
             ]
         }
     ],
+    "OmniboxSpareRenderer": [
+        {
+            "platforms": [
+                "android"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "OmniboxSpareRenderer"
+                    ]
+                }
+            ]
+        }
+    ],
     "OmniboxSuggestionsRecyclerView": [
         {
             "platforms": [