WebView: Activate AndroidWebViewConsistencyTest

This study doesn't do anything except exercise permanent-consistency.
Query it once to "activate" it, so it shows up in the logs when
WebViewLogVerbosifier.apk is installed, so QA can verify
permanent-consistency.

BUG=866722

Change-Id: I2b2c6812b735a7bd0cee8c116161d2e18c5a27f3
Reviewed-on: https://chromium-review.googlesource.com/c/1389437Reviewed-by: Changwan Ryu <changwan@chromium.org>
Commit-Queue: Paul Miller <paulmiller@chromium.org>
Cr-Commit-Position: refs/heads/master@{#619456}

android_webview/browser/aw_feature_list_creator.cc

@@ -164,6 +164,11 @@ void AwFeatureListCreator::SetUpFieldTrials() {
       std::vector<std::string>(), /*low_entropy_provider=*/nullptr,
       std::make_unique<base::FeatureList>(), aw_field_trials_.get(),
       &ignored_safe_seed_manager);
+
+  // Activate a study which exercises permanent-consistency, to test the launch
+  // of permanent-consistency support in WebView.
+  // TODO(crbug/917537): Remove this after m73.
+  base::FieldTrialList::FindFullName("AndroidWebViewConsistencyTest");
 }
 
 void AwFeatureListCreator::CreateFeatureListAndFieldTrials() {