[ChromeDriver] Fix OOPIF test flakiness on Windows

The OOPIF test is flaky on Windows due to issue chromedriver:2198,
which causes ChromeDriver not waiting for frames to fully load.
This CL adds a workaround to that issue.

Change-Id: I87c37a4c756b8a836d7d3861addb54e8bd03e853
Reviewed-on: https://chromium-review.googlesource.com/939905Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Caleb Rouleau <crouleau@chromium.org>
Commit-Queue: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#539893}

chrome/test/chromedriver/element_util.cc

@@ -257,14 +257,20 @@ Status FindElement(int interval_ms,
     arguments.Append(CreateElement(*root_element_id));
 
   base::TimeTicks start_time = base::TimeTicks::Now();
+  int context_retry = 0;
   while (true) {
     std::unique_ptr<base::Value> temp;
     Status status = web_view->CallFunction(
         session->GetCurrentFrameId(), script, arguments, &temp);
-    if (status.IsError())
+    // A "Cannot find context" error can occur due to transition from in-process
+    // iFrame to OOPIF. Retry a couple of times.
+    if (status.IsError() &&
+        (status.message().find("Cannot find context") == std::string::npos ||
+         ++context_retry > 2)) {
       return status;
+    }
 
-    if (!temp->is_none()) {
+    if (temp && !temp->is_none()) {
       if (only_one) {
         *value = std::move(temp);
         return Status(kOk);

chrome/test/chromedriver/test/run_py_tests.py

@@ -119,8 +119,6 @@ _OS_SPECIFIC_FILTER['win'] = [
     'ChromeLogPathCapabilityTest.testChromeLogPath',
     # https://bugs.chromium.org/p/chromedriver/issues/detail?id=1945
     'ChromeDriverTest.testWindowFullScreen',
-    # https://bugs.chromium.org/p/chromium/issues/detail?id=746266
-    'ChromeDriverSiteIsolation.testCanClickOOPIF',
 ]
 _OS_SPECIFIC_FILTER['linux'] = [
     # Xvfb doesn't support maximization.
@@ -1663,6 +1661,12 @@ class ChromeDriverSiteIsolation(ChromeDriverBaseTestWithWebServer):
     Note that the Iframe will not be out-of-process if the correct
     flags are not passed into Chrome.
     """
+    if util.GetPlatformName() == 'win':
+      # https://bugs.chromium.org/p/chromedriver/issues/detail?id=2198
+      # This test is unreliable on Windows, as FindElement can be called too
+      # soon, before the child frame is fully loaded. This causes element not
+      # found error. Add an implicit wait works around this issue.
+      self._driver.SetTimeout('implicit', 2000)
     self._driver.Load(self.GetHttpUrlForFile(
         '/chromedriver/cross_domain_iframe.html'))
     a_outer = self._driver.FindElement('tag name', 'a')