Revert "Ad metrics: Re-enable CreativeOrigin*Browser* tests that were flaky."

This reverts commit 8986879b.

Reason for revert: Tests are still flaky, see bug.

Original change's description:
> Ad metrics: Re-enable CreativeOrigin*Browser* tests that were flaky.
>
> Flakiness may have been fixed by
> https://chromium-review.googlesource.com/c/chromium/src/+/2290775.
> Re-enable and monitor tests for any signs of further flakiness.
>
> Bug: 1098373
> Change-Id: I3bb147b3b5fd7a1ec8fd17d99e5db44008278c80
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2391722
> Reviewed-by: Josh Karlin <jkarlin@chromium.org>
> Commit-Queue: Cammie Smith Barnes <cammie@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#810661}

TBR=jkarlin@chromium.org,cammie@chromium.org

Change-Id: I06884bc864eb74fc8c7274785f66f289ffd82093
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1098373
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2432366Reviewed-by: François Doray <fdoray@chromium.org>
Commit-Queue: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#810757}

chrome/browser/page_load_metrics/observers/ad_metrics/ads_page_load_metrics_observer_browsertest.cc

@@ -712,10 +712,11 @@ IN_PROC_BROWSER_TEST_F(CreativeOriginAdsPageLoadMetricsObserverBrowserTest,
                            OriginStatusWithThrottling::kUnknownAndUnthrottled);
 }
 
+// Flakily fails (crbug.com/1099758)
 // Test that a throttled ad with a different origin as the main page is
 // marked as throttled, with indeterminate creative origin status.
 IN_PROC_BROWSER_TEST_F(CreativeOriginAdsPageLoadMetricsObserverBrowserTest,
-                       CreativeOriginStatusWithThrottlingUnknown) {
+                       DISABLED_CreativeOriginStatusWithThrottlingUnknown) {
   TestCreativeOriginStatus(
       MakeFrame("a",
                 MakeFrame("b", MakeFrame("c", nullptr), true /* has_text */,
@@ -737,13 +738,15 @@ IN_PROC_BROWSER_TEST_F(CreativeOriginAdsPageLoadMetricsObserverBrowserTest,
       OriginStatus::kUnknown, OriginStatusWithThrottling::kUnknownAndThrottled);
 }
 
+// Flakily fails. https://crbug.com/1099545
 // Test that an ad creative with a different origin as the main page,
 // but nested in a same-origin root ad frame, such that its root ad frame
 // is outside the main frame but not throttled (because the root is
 // same-origin), will be marked as having unknown creative origin status
 // (since there will be no FCP) and being unthrottled.
-IN_PROC_BROWSER_TEST_F(CreativeOriginAdsPageLoadMetricsObserverBrowserTest,
-                       CreativeOriginStatusWithThrottlingNestedUnthrottled) {
+IN_PROC_BROWSER_TEST_F(
+    CreativeOriginAdsPageLoadMetricsObserverBrowserTest,
+    DISABLED_CreativeOriginStatusWithThrottlingNestedUnthrottled) {
   TestCreativeOriginStatus(
       MakeFrame(
           "a",