[ios] Disable failing PDF test

Test Case '-[FullscreenTestCase testLongPDFScroll]' started.
  ../../ios/chrome/test/earl_grey/chrome_earl_grey_ui.mm:207: error: -[FullscreenTestCase testLongPDFScroll] : Exception: AssertionFailedException
  Exception Name: AssertionFailedException
  Exception Reason: ((base::test::ios::WaitUntilConditionOrTimeout( kWaitForToolbarAnimationTimeout, condition)) is true) failed
  Exception Details: Toolbar was visible
  Bundle ID: org.chromium.gtest.generic-unit-test
  Stack Trace: (
  	0   EarlGrey                            0x0000000124b14446 -[GREYDefaultFailureHandler handleException:details:] + 1302
  	1   ios_chrome_ui_egtests               0x000000010e983a30 +[ChromeEarlGreyUI waitForToolbarVisible:] + 1952
  	2   ios_chrome_ui_egtests               0x000000010ea3cc9c -[FullscreenTestCase testLongPDFScroll] + 780

TBR=gambard@chromium.org, kkhorimoto@chromium.org, justincohen@chromium.org

Change-Id: Id9d1a6e9c3a3a047e9241cf5a1838721899a4fb6
Reviewed-on: https://chromium-review.googlesource.com/c/1345420Reviewed-by: edchin <edchin@chromium.org>
Commit-Queue: edchin <edchin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609876}

ios/chrome/browser/ui/fullscreen/fullscreen_egtest.mm

@@ -170,6 +170,10 @@ void AssertURLIs(const GURL& expectedURL) {
 // Verifies that the toolbar properly appears/disappears when scrolling up/down
 // on a PDF that is long in length and wide in width.
 - (void)testLongPDFScroll {
+  // TODO(crbug.com/904694): This test is failing on iOS11.
+  if (!base::ios::IsRunningOnIOS12OrLater())
+    EARL_GREY_TEST_DISABLED(@"Disabled on iOS 11.");
+
 // TODO(crbug.com/714329): Re-enable this test on devices.
 #if !TARGET_IPHONE_SIMULATOR
   EARL_GREY_TEST_DISABLED(@"Test disabled on device.");