Disable SecurityExploitBrowserTest.InvalidRequestId.

It's flaky on all operating systems and is affecting the commit queue.
Per comments on related bugs, the test is going to be removed anyway
once Chromium's network service ships.

BUG=799516
TBR=mmenke@chromium.org

Change-Id: I2813e850690ed9b162288abac3e42b3b23d33ad8
Reviewed-on: https://chromium-review.googlesource.com/866153Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#529171}

content/browser/security_exploit_browsertest.cc

@@ -506,7 +506,8 @@ IN_PROC_BROWSER_TEST_F(SecurityExploitBrowserTest, InvalidOriginHeaders) {
 
 // Renderer process should not be able to create multiple requests with the same
 // id.
-IN_PROC_BROWSER_TEST_F(SecurityExploitBrowserTest, InvalidRequestId) {
+// Disabled due to flakiness on all operating systems: crbug.com/799516
+IN_PROC_BROWSER_TEST_F(SecurityExploitBrowserTest, DISABLED_InvalidRequestId) {
   // Existing loader in pending_loaders_.
   TryCreateDuplicateRequestIds(shell(), false);
   // Existing loader in blocked_loaders_map_.