Make IsWKWebViewEnabled not query field trial, command line flags.

BUG=579249

Review URL: https://codereview.chromium.org/1625633003

Cr-Commit-Position: refs/heads/master@{#371818}

ios/chrome/browser/experimental_flags.h

@@ -28,8 +28,8 @@ void SetWKWebViewTrialEligibility(bool eligible);
 // Whether the lru snapshot cache experiment is enabled.
 bool IsLRUSnapshotCacheEnabled();
 
-// Whether the app uses WKWebView instead of UIWebView.
-// The returned value will not change within a given session.
+// TODO(crbug.com/579697): This always returns true; cleanup codepaths that use
+// this.
 bool IsWKWebViewEnabled();
 
 // Whether the user would be put into a control group for the WKWebView

ios/chrome/browser/experimental_flags.mm

@@ -143,27 +143,7 @@ bool CanCheckWKWebViewExperiment() {
 }
 
 bool IsWKWebViewEnabled() {
-  if (!CanCheckWKWebViewExperiment()) {
-    return false;
-  }
-
-  // Now that it's been established that user is a candidate, set up the trial
-  // by checking the group.
-  std::string group_name =
-      base::FieldTrialList::FindFullName(kWKWebViewTrialName);
-
-  // Check if the experimental flag is turned on.
-  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
-  if (command_line->HasSwitch(switches::kEnableIOSWKWebView))
-    return true;
-  else if (command_line->HasSwitch(switches::kDisableIOSWKWebView))
-    return false;
-
-  // Check if the finch experiment is turned on.
-  return !base::StartsWith(group_name, "Disabled",
-                           base::CompareCase::INSENSITIVE_ASCII) &&
-         !base::StartsWith(group_name, "Control",
-                           base::CompareCase::INSENSITIVE_ASCII);
+  return true;
 }
 
 bool IsTargetedToWKWebViewExperimentControlGroup() {