[ios] Remove incorrect dependency of //base//ios on //ios

Conceptually, //ios is on top of //base, so having a dependency
from //base/ios on //ios is breaking the layering (this also
make it difficult to use //base without using all of Chromium).

Implement IsMultiwindowSupported() and IsSceneStartupSupported()
by checking for the scene API manifest information in the app
Info.plist which is more robust as it will work for any iOS app
build on top of //base that set the information in Info.plist
even if they do not re-use the rest of Chromium.

Bug: none
Change-Id: I5ea006ea617c284dc114b2f8f8ecd6eb2f2dcc1d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2529122
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Mike Pinkerton <pinkerton@chromium.org>
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827759}

base/BUILD.gn

@@ -1261,10 +1261,6 @@ component("base") {
     "//third_party/modp_b64",
   ]
 
-  if (is_ios) {
-    deps += [ "//base/ios:ios_multi_window_buildflags" ]
-  }
-
   # native_unwinder_android is intended for use solely via a dynamic feature
   # module, to avoid increasing Chrome's executable size.
   assert_no_deps = [ ":native_unwinder_android" ]

base/ios/BUILD.gn

-# Copyright 2020 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.
-
-import("//build/buildflag_header.gni")
-import("//ios/build/chrome_build.gni")
-
-buildflag_header("ios_multi_window_buildflags") {
-  header = "multi_window_buildflags.h"
-  header_dir = "base/ios"
-  flags = [
-    "IOS_MULTIWINDOW_ENABLED=$ios_enable_multi_window",
-    "IOS_SCENE_STARTUP_ENABLED=$ios_enable_scene_startup",
-  ]
-}

base/ios/ios_util.mm

@@ -7,12 +7,20 @@
 #import <Foundation/Foundation.h>
 #include <stddef.h>
 
-#include "base/ios/multi_window_buildflags.h"
+#include "base/mac/foundation_util.h"
 #include "base/stl_util.h"
 #include "base/system/sys_info.h"
 
 namespace {
 
+// Key for the scene API manifest in the application Info.plist.
+NSString* const kApplicationSceneManifestKey = @"UIApplicationSceneManifest";
+
+// Key for the boolean telling whether the multi-scene support is enabled for
+// the application in the scene API manifest.
+NSString* const kApplicationSupportsMultipleScenesKey =
+    @"UIApplicationSupportsMultipleScenes";
+
 // Return a 3 elements array containing the major, minor and bug fix version of
 // the OS.
 const int32_t* OSVersionAsArray() {
@@ -22,6 +30,19 @@ const int32_t* OSVersionAsArray() {
   return digits;
 }
 
+// Return an autoreleased pointer to the dictionary configuring the scene API
+// from the application Info.plist. Can be null if the application or the OS
+// version does not use the scene API.
+NSDictionary* SceneAPIManifestFromInfoPlist() {
+  // Scene API is only supported on iOS 13.0+.
+  if (!base::ios::IsRunningOnIOS13OrLater())
+    return nil;
+
+  NSBundle* main_bundle = [NSBundle mainBundle];
+  return base::mac::ObjCCastStrict<NSDictionary>(
+      [main_bundle objectForInfoDictionaryKey:kApplicationSceneManifestKey]);
+}
+
 std::string* g_icudtl_path_override = nullptr;
 
 }  // namespace
@@ -72,21 +93,25 @@ FilePath FilePathOfEmbeddedICU() {
 }
 
 bool IsMultiwindowSupported() {
-#if BUILDFLAG(IOS_MULTIWINDOW_ENABLED)
-  return IsRunningOnIOS13OrLater();
-#else
-  return false;
-#endif
+  static bool cached_value = false;
+  static dispatch_once_t once_token = 0;
+  dispatch_once(&once_token, ^{
+    NSDictionary* scene_api_manifest = SceneAPIManifestFromInfoPlist();
+    NSNumber* value = base::mac::ObjCCastStrict<NSNumber>([scene_api_manifest
+        objectForKey:kApplicationSupportsMultipleScenesKey]);
+    cached_value = [value boolValue];
+  });
+  return cached_value;
 }
 
 bool IsSceneStartupSupported() {
-  if (IsMultiwindowSupported())
-    return true;
-#if BUILDFLAG(IOS_SCENE_STARTUP_ENABLED)
-  return base::ios::IsRunningOnIOS13OrLater();
-#else
-  return false;
-#endif
+  static bool cached_value = false;
+  static dispatch_once_t once_token = 0;
+  dispatch_once(&once_token, ^{
+    NSDictionary* scene_api_manifest = SceneAPIManifestFromInfoPlist();
+    cached_value = scene_api_manifest != nil;
+  });
+  return cached_value;
 }
 
 }  // namespace ios

ios/chrome/app/BUILD.gn

@@ -170,9 +170,9 @@ source_set("app_internal") {
     ":blocking_scene_commands",
     ":content_suggestions_scheduler_app_state_agent",
     ":mode",
+    ":multi_window_buildflags",
     ":tests_hook",
     "//base",
-    "//base/ios:ios_multi_window_buildflags",
     "//build:branding_buildflags",
     "//components/bookmarks/browser",
     "//components/browser_sync",
@@ -303,6 +303,11 @@ source_set("app_internal") {
   ]
 }
 
+buildflag_header("multi_window_buildflags") {
+  header = "multi_window_buildflags.h"
+  flags = [ "IOS_MULTIWINDOW_ENABLED=$ios_enable_multi_window" ]
+}
+
 source_set("blocking_scene_commands") {
   configs += [ "//build/config/compiler:enable_arc" ]
   sources = [ "blocking_scene_commands.h" ]

ios/chrome/app/main_application_delegate.mm

@@ -5,7 +5,6 @@
 #import "ios/chrome/app/main_application_delegate.h"
 
 #include "base/ios/ios_util.h"
-#include "base/ios/multi_window_buildflags.h"
 #include "base/mac/foundation_util.h"
 #include "base/metrics/user_metrics.h"
 #import "ios/chrome/app/application_delegate/app_state.h"
@@ -21,6 +20,7 @@
 #import "ios/chrome/app/chrome_overlay_window.h"
 #import "ios/chrome/app/main_application_delegate_testing.h"
 #import "ios/chrome/app/main_controller.h"
+#include "ios/chrome/app/multi_window_buildflags.h"
 #import "ios/chrome/browser/ui/main/scene_controller.h"
 #import "ios/chrome/browser/ui/main/scene_delegate.h"
 #import "ios/chrome/browser/ui/main/scene_state.h"

ios/chrome/browser/ui/main/incognito_blocker_scene_agent.mm

@@ -76,7 +76,7 @@
 - (void)showOverlay {
   NSArray<UIWindow*>* windows = nil;
 
-  if (IsMultiwindowSupported()) {
+  if (IsSceneStartupSupported()) {
     if (@available(iOS 13, *)) {
       windows = self.sceneState.scene.windows;
     }

ios/chrome/browser/ui/util/BUILD.gn

@@ -13,10 +13,7 @@ source_set("multiwindow_util") {
     "multi_window_support.mm",
   ]
 
-  deps = [
-    "//base",
-    "//base/ios:ios_multi_window_buildflags",
-  ]
+  deps = [ "//base" ]
 }
 
 source_set("util") {