Revert "Enable WebNavigationApiTest.CrossProcess(History|Fragment)."

This reverts commit e03b42cc.

Reason for revert: both tests timeout quite reliably on Win10 Tests x64 (https://build.chromium.org/p/chromium.win/builders/Win10%20Tests%20x64/builds/14362)

Original change's description:
> Enable WebNavigationApiTest.CrossProcess(History|Fragment).
> 
> Bug: 708139
> Change-Id: Idb9eb18755219be4164b6fc2585aa43ed9798dc1
> Reviewed-on: https://chromium-review.googlesource.com/601027
> Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
> Commit-Queue: Nasko Oskov <nasko@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#491836}

TBR=nasko@chromium.org,alexmos@chromium.org

Change-Id: Iee6a4124181b0e7761a5c77e1f65ea3cda23d4d8
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 708139
Reviewed-on: https://chromium-review.googlesource.com/601948Reviewed-by: Vasilii Sukhanov <vasilii@chromium.org>
Commit-Queue: Vasilii Sukhanov <vasilii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491976}

chrome/browser/extensions/api/web_navigation/web_navigation_apitest.cc

@@ -714,7 +714,8 @@ IN_PROC_BROWSER_TEST_F(WebNavigationApiTest, CrossProcessAbort) {
   ASSERT_TRUE(catcher.GetNextResult()) << catcher.message();
 }
 
-IN_PROC_BROWSER_TEST_F(WebNavigationApiTest, CrossProcessFragment) {
+// crbug.com/708139.
+IN_PROC_BROWSER_TEST_F(WebNavigationApiTest, DISABLED_CrossProcessFragment) {
   ASSERT_TRUE(StartEmbeddedTestServer());
 
   // See crossProcessFragment/f.html.
@@ -735,7 +736,8 @@ IN_PROC_BROWSER_TEST_F(WebNavigationApiTest, CrossProcessFragment) {
       << message_;
 }
 
-IN_PROC_BROWSER_TEST_F(WebNavigationApiTest, CrossProcessHistory) {
+// crbug.com/708139.
+IN_PROC_BROWSER_TEST_F(WebNavigationApiTest, DISABLED_CrossProcessHistory) {
   ASSERT_TRUE(StartEmbeddedTestServer());
 
   // See crossProcessHistory/e.html.