[iOS] Upstream switches and flags controlling which WebView is used

Which of UIWebView and WKWebView to use can be controller by command line
flags, finch and availability (iOS version).

BUG=429756

Review URL: https://codereview.chromium.org/1144803002

Cr-Commit-Position: refs/heads/master@{#330383}

ios/chrome/browser/chrome_switches.cc

@@ -12,9 +12,15 @@ namespace switches {
 // all work out.
 // -----------------------------------------------------------------------------
 
+// Disables the use of WKWebView instead of UIWebView.
+const char kDisableIOSWKWebView[] = "disable-wkwebview";
+
 // Enables Open from Clipboard.
 const char kEnableIOSOpenFromClipboard[] = "enable-ios-open-from-clipboard";
 
+// Enables the use of WKWebView instead of UIWebView.
+const char kEnableIOSWKWebView[] = "enable-wkwebview";
+
 // Defines the value in MB of the memory wedge to insert at cold launch.
 const char kIOSMemoryWedgeSize[] = "ios-memory-wedge-size-mb";
 

ios/chrome/browser/chrome_switches.h

@@ -9,8 +9,9 @@
 
 namespace switches {
 
+extern const char kDisableIOSWKWebView[];
 extern const char kEnableIOSOpenFromClipboard[];
-
+extern const char kEnableIOSWKWebView[];
 extern const char kIOSMemoryWedgeSize[];
 
 }  // namespace switches

ios/chrome/browser/experimental_flags.h

@@ -18,6 +18,9 @@ bool IsAlertOnBackgroundUploadEnabled();
 // Returns true if the contents of the clipboard can be used for autocomplete.
 bool IsOpenFromClipboardEnabled();
 
+// Whether the app uses WKWebView instead of UIWebView.
+bool IsWKWebViewEnabled();
+
 // Returns the size in MB of the memory wedge to insert during a cold start.
 // If 0, no memory wedge should be inserted.
 size_t MemoryWedgeSizeInMB();

ios/chrome/browser/experimental_flags.mm

@@ -12,8 +12,10 @@
 #include "base/command_line.h"
 #include "base/metrics/field_trial.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/strings/string_util.h"
 #include "components/variations/variations_associated_data.h"
 #include "ios/chrome/browser/chrome_switches.h"
+#include "ios/web/public/web_view_util.h"
 
 namespace {
 NSString* const kEnableAlertOnBackgroundUpload =
@@ -32,6 +34,28 @@ bool IsOpenFromClipboardEnabled() {
   return command_line->HasSwitch(switches::kEnableIOSOpenFromClipboard);
 }
 
+bool IsWKWebViewEnabled() {
+  // If WKWebView isn't supported, don't activate the experiment at all. This
+  // avoids someone being slotted into the WKWebView bucket (and thus reporting
+  // as WKWebView), but actually running UIWebView.
+  if (!web::IsWKWebViewSupported())
+    return false;
+
+  std::string group_name =
+      base::FieldTrialList::FindFullName("IOSUseWKWebView");
+
+  // First 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 StartsWithASCII(group_name, "Enabled", false);
+}
+
 size_t MemoryWedgeSizeInMB() {
   std::string wedge_size_string;
 

ios/chrome/browser/web/web_view_type_util.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef IOS_CHROME_BROWSER_WEB_WEB_VIEW_TYPE_UTIL_H_
+#define IOS_CHROME_BROWSER_WEB_WEB_VIEW_TYPE_UTIL_H_
+
+#include "ios/web/public/web_view_type.h"
+
+// Utilities for getting the web view type to use in the application, or to
+// wrap web view creation APIs with versions that automatically select the
+// right type.
+namespace web_view_type_util {
+
+// Returns the type to use for all web views in the application.
+web::WebViewType GetWebViewType();
+
+}  // web_view_type_util
+
+#endif  // IOS_CHROME_BROWSER_WEB_WEB_VIEW_TYPE_UTIL_H_

ios/chrome/browser/web/web_view_type_util.mm

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ios/chrome/browser/web/web_view_type_util.h"
+
+#include "ios/chrome/browser/experimental_flags.h"
+
+namespace web_view_type_util {
+
+web::WebViewType GetWebViewType() {
+  return experimental_flags::IsWKWebViewEnabled() ? web::WK_WEB_VIEW_TYPE
+                                                  : web::UI_WEB_VIEW_TYPE;
+}
+
+}  // namespace web_view_type_util

ios/chrome/ios_chrome.gyp

@@ -271,6 +271,8 @@
         'browser/updatable_config/updatable_dictionary.mm',
         'browser/web/dom_altering_lock.h',
         'browser/web/dom_altering_lock.mm',
+        'browser/web/web_view_type_util.h',
+        'browser/web/web_view_type_util.mm',
         'browser/web_resource/ios_web_resource_service.cc',
         'browser/web_resource/ios_web_resource_service.h',
         'browser/xcallback_parameters.h',