Prepare WebUIMojoTest for Pending Item ownership refactoring.

Notable changes:
 - SetUp method wraps it's code into @autoreleasepool, to make sure that
   CRWWebController never goes to autorelease pool. CRWWebController
   will go to autorelease pool when used as a delegate for
   CRWSessionController in crrev.com/1455658. CRWWebController should
   not outlive WebThreadBundle, hence should not go to autorelease pool.

 - Use public WebState API for web state creation. This way all requred
   changes inside WebState::Create don't have to be duplicated in
   the test, which used to create WebStateImpl object via constructor.

Bug: 899827
Change-Id: I50d07c6a06c5affdab2aa0924d3c97f15b4c387e
Reviewed-on: https://chromium-review.googlesource.com/c/1484819
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Auto-Submit: Eugene But <eugenebut@chromium.org>
Reviewed-by: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#634984}

ios/web/webui/web_ui_mojo_inttest.mm

@@ -11,6 +11,7 @@
 #include "ios/web/grit/ios_web_resources.h"
 #import "ios/web/public/navigation_manager.h"
 #import "ios/web/public/test/navigation_test_util.h"
+#import "ios/web/public/web_state/web_state.h"
 #include "ios/web/public/web_state/web_state_interface_provider.h"
 #include "ios/web/public/web_ui_ios_data_source.h"
 #include "ios/web/public/webui/web_ui_ios_controller.h"
@@ -19,8 +20,6 @@
 #include "ios/web/test/mojo_test.mojom.h"
 #include "ios/web/test/test_url_constants.h"
 #import "ios/web/test/web_int_test.h"
-#import "ios/web/web_state/ui/crw_web_controller.h"
-#import "ios/web/web_state/web_state_impl.h"
 #include "mojo/public/cpp/bindings/binding_set.h"
 #include "url/gurl.h"
 #include "url/scheme_host_port.h"
@@ -143,12 +142,13 @@ class WebUIMojoTest : public WebIntTest {
  protected:
   void SetUp() override {
     WebIntTest::SetUp();
-    ui_handler_ = std::make_unique<TestUIHandler>();
-    web::WebState::CreateParams params(GetBrowserState());
-    web_state_ = std::make_unique<web::WebStateImpl>(params);
-    web_state_->GetNavigationManagerImpl().InitializeSession();
-    WebUIIOSControllerFactory::RegisterFactory(
-        new TestWebUIControllerFactory(ui_handler_.get()));
+    @autoreleasepool {
+      ui_handler_ = std::make_unique<TestUIHandler>();
+      WebState::CreateParams params(GetBrowserState());
+      web_state_ = WebState::Create(params);
+      WebUIIOSControllerFactory::RegisterFactory(
+          new TestWebUIControllerFactory(ui_handler_.get()));
+    }
   }
 
   void TearDown() override {
@@ -169,12 +169,12 @@ class WebUIMojoTest : public WebIntTest {
   }
 
   // Returns WebState which loads test WebUI page.
-  WebStateImpl* web_state() { return web_state_.get(); }
+  WebState* web_state() { return web_state_.get(); }
   // Returns UI handler which communicates with WebUI page.
   TestUIHandler* test_ui_handler() { return ui_handler_.get(); }
 
  private:
-  std::unique_ptr<WebStateImpl> web_state_;
+  std::unique_ptr<WebState> web_state_;
   std::unique_ptr<TestUIHandler> ui_handler_;
 };