AW UMA: enable WebViewWakeMetricsService by default

No change to logic. This enables WebViewWakeMetricsService by default,
per go/finch-best-practices. This switch will be removed in a future CL.

Bug: 1003204
Test: CQ
Change-Id: I7ff2554fd24839a32a986ec0ef3eb5ae45a9f6ec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2161615
Auto-Submit: Nate Fischer <ntfschr@chromium.org>
Reviewed-by: Changwan Ryu <changwan@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Commit-Queue: Jesse Doherty <jwd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#762145}

android_webview/common/aw_features.cc

@@ -34,7 +34,7 @@ const base::Feature kWebViewSniffMimeType{"WebViewSniffMimeType",
 // Wake up the MetricsService for each page load start/finish, renderer hang,
 // and renderer close. This aligns with Chrome's behavior.
 const base::Feature kWebViewWakeMetricsService{
-    "WebViewWakeMetricsService", base::FEATURE_DISABLED_BY_DEFAULT};
+    "WebViewWakeMetricsService", base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Enable raster in wide color gamut for apps that use webview in a wide color
 // gamut activity.

testing/variations/fieldtrial_testing_config.json

@@ -6976,21 +6976,6 @@
             ]
         }
     ],
-    "WebViewWakeMetricsService": [
-        {
-            "platforms": [
-                "android_webview"
-            ],
-            "experiments": [
-                {
-                    "name": "Enabled",
-                    "enable_features": [
-                        "WebViewWakeMetricsService"
-                    ]
-                }
-            ]
-        }
-    ],
     "WebXrPermissionsApi": [
         {
             "platforms": [