[ios] Add experiment flag for WKWebView snapshotting

This CL simply adds the flag so that it can be used in
a future CL. This flag controls whether the WKWebView
snapshotting API is used to take snapshots for web pages
(not native pages) on iOS 11+.

The crbug to remove the flag is crbug.com/885003.

Bug: 739840
Cq-Include-Trybots: luci.chromium.try:ios-simulator-cronet;luci.chromium.try:ios-simulator-full-configs
Change-Id: Id00c4da93f5046e4a2b2af179abe3794a99a248e
Reviewed-on: https://chromium-review.googlesource.com/1229703
Commit-Queue: edchin <edchin@chromium.org>
Reviewed-by: edchin <edchin@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592108}

ios/chrome/app/tests_fake_hook.mm

@@ -34,6 +34,10 @@ bool DisableUpdateService() {
 bool ForceUIRefreshPhase1() {
   return false;
 }
+// TODO(crbug.com/885003) : Remove this hook.
+bool ForceWKWebViewSnapshots() {
+  return false;
+}
 void SetUpTestsIfPresent() {}
 void RunTestsIfPresent() {}
 

ios/chrome/app/tests_hook.h

@@ -41,6 +41,11 @@ bool DisableUpdateService();
 // overriding the flag value.
 bool ForceUIRefreshPhase1();
 
+// TODO(crbug.com/885003) : Remove this hook.
+// Returns true if the WKWebView snapshotting API will be used, overriding the
+// flag value.
+bool ForceWKWebViewSnapshots();
+
 // Global integration tests setup.  This is not used by EarlGrey-based
 // integration tests.
 void SetUpTestsIfPresent();

ios/chrome/browser/about_flags.mm

@@ -387,6 +387,9 @@ const flags_ui::FeatureEntry kFeatureEntries[] = {
     {"sso-with-wkwebview", flag_descriptions::kSSOWithWKWebViewName,
      flag_descriptions::kSSOWithWKWebViewDescription, flags_ui::kOsIos,
      FEATURE_VALUE_TYPE(kSSOWithWKWebView)},
+    {"wk-web-view-snapshots", flag_descriptions::kWKWebViewSnapshotsName,
+     flag_descriptions::kWKWebViewSnapshotsDescription, flags_ui::kOsIos,
+     FEATURE_VALUE_TYPE(kWKWebViewSnapshots)},
 };
 
 // Add all switches from experimental flags to |command_line|.

ios/chrome/browser/ios_chrome_flag_descriptions.cc

@@ -295,6 +295,10 @@ const char kWKHTTPSystemCookieStoreName[] = "Use WKHTTPSystemCookieStore.";
 const char kWKHTTPSystemCookieStoreDescription[] =
     "Use WKHTTPCookieStore backed store for main context URL requests.";
 
+const char kWKWebViewSnapshotsName[] = "WKWebView Snapshots";
+const char kWKWebViewSnapshotsDescription[] =
+    "When enabled, the WKWebView snapshotting API is used for iOS 11+.";
+
 // Please insert your name/description above in alphabetical order.
 
 }  // namespace flag_descriptions

ios/chrome/browser/ios_chrome_flag_descriptions.h

@@ -246,6 +246,10 @@ extern const char kWebPaymentsNativeAppsDescription[];
 extern const char kWKHTTPSystemCookieStoreName[];
 extern const char kWKHTTPSystemCookieStoreDescription[];
 
+// Title and description for the flag to use the WKWebView snapshotting API.
+extern const char kWKWebViewSnapshotsName[];
+extern const char kWKWebViewSnapshotsDescription[];
+
 // Please insert your name/description above in alphabetical order.
 
 }  // namespace flag_descriptions

ios/chrome/browser/ui/tab_grid/tab_grid_egtests_hook.mm

@@ -42,6 +42,11 @@ bool ForceUIRefreshPhase1() {
   return true;
 }
 
+// TODO(crbug.com/885003) : Remove this hook.
+bool ForceWKWebViewSnapshots() {
+  return false;
+}
+
 void SetUpTestsIfPresent() {
   // No-op for Earl Grey.
 }

ios/chrome/browser/ui/toolbar/adaptive/adaptive_toolbar_eg_tests_hook.mm

@@ -42,6 +42,11 @@ bool ForceUIRefreshPhase1() {
   return true;
 }
 
+// TODO(crbug.com/885003) : Remove this hook.
+bool ForceWKWebViewSnapshots() {
+  return false;
+}
+
 void SetUpTestsIfPresent() {
   // No-op for Earl Grey.
 }

ios/chrome/browser/ui/ui_feature_flags.cc

@@ -8,3 +8,6 @@ const base::Feature kFirstResponderKeyWindow{"FirstResponderKeyWindow",
                                              base::FEATURE_ENABLED_BY_DEFAULT};
 
 const base::Feature kCopyImage{"CopyImage", base::FEATURE_ENABLED_BY_DEFAULT};
+
+const base::Feature kWKWebViewSnapshots{"WKWebViewSnapshots",
+                                        base::FEATURE_DISABLED_BY_DEFAULT};

ios/chrome/browser/ui/ui_feature_flags.h

@@ -15,4 +15,7 @@ extern const base::Feature kFirstResponderKeyWindow;
 // Feature to copy image to system pasteboard via context menu.
 extern const base::Feature kCopyImage;
 
+// Used to enable using the WKWebView snapshotting API for iOS 11+.
+extern const base::Feature kWKWebViewSnapshots;
+
 #endif  // IOS_CHROME_BROWSER_UI_UI_FEATURE_FLAGS_H_

ios/chrome/browser/ui/ui_util.h

@@ -55,6 +55,9 @@ bool IsRefreshPopupPresentationEnabled();
 // TODO (crbug.com/884725): Remove all use of this flag.
 bool IsUIRefreshPhase1Enabled();
 
+// Returns whether the WKWebView snapshotting API will be used for iOS 11+.
+bool IsWKWebViewSnapshotsEnabled();
+
 // Returns the height of the status bar, accounting for orientation.
 CGFloat StatusBarHeight();
 

ios/chrome/browser/ui/ui_util.mm

@@ -74,6 +74,13 @@ bool IsUIRefreshPhase1Enabled() {
   return true;
 }
 
+// TODO(crbug.com/885003) : Remove this flag.
+bool IsWKWebViewSnapshotsEnabled() {
+  if (tests_hook::ForceWKWebViewSnapshots())
+    return true;
+  return base::FeatureList::IsEnabled(kWKWebViewSnapshots);
+}
+
 CGFloat StatusBarHeight() {
   // This is a temporary solution until usage of StatusBarHeight has been
   // replaced with topLayoutGuide.

ios/chrome/test/earl_grey/eg_tests_hook.mm

@@ -42,6 +42,11 @@ bool ForceUIRefreshPhase1() {
   return false;
 }
 
+// TODO(crbug.com/885003) : Remove this hook.
+bool ForceWKWebViewSnapshots() {
+  return false;
+}
+
 void SetUpTestsIfPresent() {
   // No-op for Earl Grey.
 }