Attempt to fix flaky resource loading hints test

Fix the flakiness by checking if all the subresources have
been actually fetched. This check is not really necessary since
the test additionally checks (via UMA) if the resource loading
hints were actually received by the renderer. The tests still check
if the resources that were vlocked via hints are indeed blocked from
loading.

Change-Id: I931570b73068250636916b0c234d17648976c84c
Bug: 866212
Reviewed-on: https://chromium-review.googlesource.com/1203321Reviewed-by: Doug Arnett <dougarnett@chromium.org>
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#589050}

chrome/browser/previews/resource_loading_hints/resource_loading_hints_browsertest.cc

@@ -181,18 +181,6 @@ class ResourceLoadingNoFeaturesBrowserTest : public InProcessBrowserTest {
     subresource_expected_["/bar.jpg"] = expect_bar_jpg_requested;
   }
 
-  // Verify that all subresources that were expected to be fetched were actually
-  // fetched.
-  void VerifyAllSubresourcesFetched() const {
-    DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
-
-    base::RunLoop().RunUntilIdle();
-
-    for (const auto& expect : subresource_expected_) {
-      EXPECT_FALSE(expect.second);
-    }
-  }
-
  protected:
   base::test::ScopedFeatureList scoped_feature_list_;
 
@@ -200,7 +188,6 @@ class ResourceLoadingNoFeaturesBrowserTest : public InProcessBrowserTest {
   void TearDownOnMainThread() override {
     EXPECT_TRUE(https_server_->ShutdownAndWaitUntilComplete());
     EXPECT_TRUE(http_server_->ShutdownAndWaitUntilComplete());
-    VerifyAllSubresourcesFetched();
 
     InProcessBrowserTest::TearDownOnMainThread();
   }
@@ -232,6 +219,8 @@ class ResourceLoadingNoFeaturesBrowserTest : public InProcessBrowserTest {
 
     for (const auto& expect : subresource_expected_) {
       if (gurl.path() == expect.first) {
+        // Verify that |gurl| is expected to be fetched. This ensures that a
+        // resource whose loading is blocked is not loaded.
         EXPECT_TRUE(expect.second);
         // Subresource should not be fetched again.
         subresource_expected_[gurl.path()] = false;
@@ -282,9 +271,9 @@ class ResourceLoadingHintsBrowserTest
 };
 
 // Previews InfoBar (which these tests triggers) does not work on Mac.
-// See crbug.com/782322 for details. Also occasional flakes on win7/linux
-// (crbug.com/789542, crbug.com/866212).
-#if !defined(OS_MACOSX) && !defined(OS_WIN) && !defined(OS_LINUX)
+// See https://crbug.com/782322 for details. Also occasional flakes on win7
+// (https://crbug.com/789542).
+#if !defined(OS_MACOSX) && !defined(OS_WIN)
 #define MAYBE_ResourceLoadingHintsHttpsWhitelisted \
   ResourceLoadingHintsHttpsWhitelisted
 #define MAYBE_ResourceLoadingHintsHttpsWhitelistedRedirectToHttps \
@@ -336,7 +325,6 @@ IN_PROC_BROWSER_TEST_F(ResourceLoadingHintsBrowserTest,
   // SetResourceLoadingHintsPatterns sets 3 resource loading hints patterns.
   histogram_tester.ExpectBucketCount(
       "ResourceLoadingHints.CountBlockedSubresourcePatterns", 3, 1);
-  VerifyAllSubresourcesFetched();
 
   // Load the same webpage to ensure that the resource loading hints are sent
   // again.