[Reland] Block resources in FormStructureBrowserTest.

The files used for FormStructureBrowserTest are snapshots of real web
sites. They can have link to online resources but should not need them
for the test to pass.
But if the network is really bad, the page can wait for the resource
loading to finish and timeout.
Preventing the resource loading will make the test faster and more
robust.

Bug: 896173
Change-Id: I16b02e1d7defd4d950e6ee4cd21bd0133b9ac957
Reviewed-on: https://chromium-review.googlesource.com/c/1346462
Commit-Queue: Olivier Robin <olivierrobin@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610366}

ios/chrome/browser/autofill/form_structure_browsertest.mm

@@ -165,7 +165,7 @@ void FormStructureBrowserTest::TearDown() {
 
 void FormStructureBrowserTest::GenerateResults(const std::string& input,
                                                std::string* output) {
-  ASSERT_TRUE(LoadHtml(input));
+  ASSERT_TRUE(LoadHtmlWithoutSubresources(input));
   base::TaskScheduler::GetInstance()->FlushForTesting();
   web::WebFrame* frame = web::GetMainWebFrame(web_state());
   AutofillManager* autofill_manager =

ios/web/public/test/web_test_with_web_state.h

@@ -47,6 +47,11 @@ class WebTestWithWebState : public WebTest,
   void LoadHtml(NSString* html);
   // Loads the specified HTML content into the WebState, using test url name.
   bool LoadHtml(const std::string& html) WARN_UNUSED_RESULT;
+  // Loads the specified HTML content with URL into the WebState. None of the
+  // subresources will be fetched.
+  // This function is only supported on iOS11+. On iOS10, this function simply
+  // calls |LoadHtml|.
+  bool LoadHtmlWithoutSubresources(const std::string& html);
   // Blocks until both known NSRunLoop-based and known message-loop-based
   // background tasks have completed
   void WaitForBackgroundTasks();

ios/web/public/test/web_test_with_web_state.mm

@@ -4,6 +4,7 @@
 
 #import "ios/web/public/test/web_test_with_web_state.h"
 
+#include "base/ios/ios_util.h"
 #include "base/message_loop/message_loop_current.h"
 #include "base/run_loop.h"
 #include "base/scoped_observer.h"
@@ -15,6 +16,7 @@
 #include "ios/web/public/web_state/url_verification_constants.h"
 #include "ios/web/public/web_state/web_state_observer.h"
 #import "ios/web/web_state/ui/crw_web_controller.h"
+#import "ios/web/web_state/ui/wk_web_view_configuration_provider.h"
 #import "ios/web/web_state/web_state_impl.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
@@ -22,6 +24,7 @@
 #endif
 
 using base::test::ios::WaitUntilConditionOrTimeout;
+using base::test::ios::kWaitForActionTimeout;
 using base::test::ios::kWaitForJSCompletionTimeout;
 using base::test::ios::kWaitForPageLoadTimeout;
 
@@ -75,6 +78,56 @@ void WebTestWithWebState::AddTransientItem(const GURL& url) {
       .AddTransientItem(url);
 }
 
+bool WebTestWithWebState::LoadHtmlWithoutSubresources(const std::string& html) {
+  if (@available(iOS 11, *)) {
+    NSString* block_all = @"[{"
+                           "  \"trigger\": {"
+                           "    \"url-filter\": \".*\""
+                           "  },"
+                           "  \"action\": {"
+                           "    \"type\": \"block\""
+                           "  }"
+                           "}]";
+    __block WKContentRuleList* content_rule_list = nil;
+    __block NSError* error = nil;
+    __block BOOL rule_compilation_completed = NO;
+    [WKContentRuleListStore.defaultStore
+        compileContentRuleListForIdentifier:@"block_everything"
+                     encodedContentRuleList:block_all
+                          completionHandler:^(WKContentRuleList* rule_list,
+                                              NSError* err) {
+                            error = err;
+                            content_rule_list = rule_list;
+                            rule_compilation_completed = YES;
+                          }];
+
+    bool success = WaitUntilConditionOrTimeout(kWaitForActionTimeout, ^{
+      return rule_compilation_completed;
+    });
+    if (!success) {
+      DLOG(WARNING) << "ContentRuleList compilation timed out.";
+      return false;
+    }
+    if (error) {
+      DLOG(WARNING) << "ContentRuleList compilation failed with error: "
+                    << base::SysNSStringToUTF8(error.description);
+      return false;
+    }
+    DCHECK(content_rule_list);
+    WKWebViewConfigurationProvider& configuration_provider =
+        web::WKWebViewConfigurationProvider::FromBrowserState(
+            GetBrowserState());
+    WKWebViewConfiguration* configuration =
+        configuration_provider.GetWebViewConfiguration();
+    [configuration.userContentController addContentRuleList:content_rule_list];
+    bool result = LoadHtml(html);
+    [configuration.userContentController
+        removeContentRuleList:content_rule_list];
+    return result;
+  }
+  return LoadHtml(html);
+}
+
 void WebTestWithWebState::LoadHtml(NSString* html, const GURL& url) {
   // Sets MIME type to "text/html" once navigation is committed.
   class MimeTypeUpdater : public WebStateObserver {