Disable IgnoresChildFrameNavigation due to flakes.

Bug: 1009465
TBR: mdjones@chromium.org
Change-Id: I40d0a3919d92e02d885648707569735f3cf80d83
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1831448Reviewed-by: Frank Liberato <liberato@chromium.org>
Commit-Queue: Frank Liberato <liberato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#701164}

components/dom_distiller/content/browser/web_contents_main_frame_observer_unittest.cc

@@ -59,7 +59,7 @@ TEST_F(WebContentsMainFrameObserverTest, ListensForMainFrameNavigation) {
   EXPECT_TRUE(main_frame_observer_->is_document_loaded_in_main_frame());
 }
 
-TEST_F(WebContentsMainFrameObserverTest, IgnoresChildFrameNavigation) {
+TEST_F(WebContentsMainFrameObserverTest, DISABLED_IgnoresChildFrameNavigation) {
   Navigate(kChildFrame, kDifferentDocument);
   EXPECT_FALSE(main_frame_observer_->is_initialized());
   EXPECT_FALSE(main_frame_observer_->is_document_loaded_in_main_frame());