Fix flaky test *NetworkIsolationKeyReusedForBackNavigation*

It's suspected that there could be another request coming to the
completion callback, between the final navigation request and the final
assertion. Checking the URL in the completion callback to make sure we
are checking the cache status of the navigation request.

Bug: 1024033
Change-Id: I200f5c44ba72e6abcff7468f0e037a97cdf4fc53
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2087736Reviewed-by: Matt Menke <mmenke@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Yao Xiao <yaoxia@chromium.org>
Cr-Commit-Position: refs/heads/master@{#747053}

chrome/browser/tab_contents/view_source_browsertest.cc

@@ -531,10 +531,8 @@ using ViewSourceWithSplitCacheEnabledTest = ViewSourceWithSplitCacheTest;
 // In the end, the test checks whether the back navigation request resource
 // exists in the cache. |exists_in_cache == true| implies the top_frame_origin
 // of the network isolation key is a.com (reused).
-//
-// Flaky. http://crbug.com/1024033
 IN_PROC_BROWSER_TEST_P(ViewSourceWithSplitCacheEnabledTest,
-                       DISABLED_NetworkIsolationKeyReusedForBackNavigation) {
+                       NetworkIsolationKeyReusedForBackNavigation) {
   content::SetupCrossSiteRedirector(embedded_test_server());
   ASSERT_TRUE(embedded_test_server()->Start());
 
@@ -545,10 +543,10 @@ IN_PROC_BROWSER_TEST_P(ViewSourceWithSplitCacheEnabledTest,
   content::WebContents* original_contents =
       browser()->tab_strip_model()->GetActiveWebContents();
 
+  std::string subframe_url =
+      GURL(embedded_test_server()->GetURL("b.com", "/title1.html")).spec();
   {
     // 2. Create a cross-site subframe b.com/title1.html
-    std::string subframe_url =
-        GURL(embedded_test_server()->GetURL("b.com", "/title1.html")).spec();
     std::string create_frame_script = base::StringPrintf(
         "let frame = document.createElement('iframe');"
         "frame.src = '%s';"
@@ -578,7 +576,7 @@ IN_PROC_BROWSER_TEST_P(ViewSourceWithSplitCacheEnabledTest,
   ui_test_utils::NavigateToURL(
       browser(), GURL(embedded_test_server()->GetURL("c.com", "/title1.html")));
 
-  bool exists_in_cache = false;
+  base::RunLoop cache_status_waiter;
   content::URLLoaderInterceptor interceptor(
       base::BindLambdaForTesting(
           [&](content::URLLoaderInterceptor::RequestParams* params) {
@@ -587,7 +585,10 @@ IN_PROC_BROWSER_TEST_P(ViewSourceWithSplitCacheEnabledTest,
       base::BindLambdaForTesting(
           [&](const GURL& request_url,
               const network::URLLoaderCompletionStatus& status) {
-            exists_in_cache = status.exists_in_cache;
+            if (request_url == subframe_url) {
+              EXPECT_TRUE(status.exists_in_cache);
+              cache_status_waiter.Quit();
+            }
           }),
       {});
 
@@ -600,7 +601,7 @@ IN_PROC_BROWSER_TEST_P(ViewSourceWithSplitCacheEnabledTest,
     navigation_observer.Wait();
   }
 
-  EXPECT_TRUE(exists_in_cache);
+  cache_status_waiter.Run();
 }
 
 INSTANTIATE_TEST_SUITE_P(