Revert "Remove unnecessary tab key press from Focus_AdvanceFocus test"

This reverts commit 5eeadd14.

Reason for revert: Seems to have caused failures on mac_cocoa_rel, see e.g. https://logs.chromium.org/logs/chromium/buildbucket/cr-buildbucket.appspot.com/8938549477439492256/+/steps/interactive_ui_tests/0/logs/WebViewFocusInteractiveTest.Focus_AdvanceFocus/0

Original change's description:
> Remove unnecessary tab key press from Focus_AdvanceFocus test
> 
> The associated bug which required this extra tab is fixed.
> 
> Bug: 147644
> Change-Id: Ied21533accc82613053e119aa2c5c64fc9de8343
> Reviewed-on: https://chromium-review.googlesource.com/1170986
> Reviewed-by: Ehsan Karamad <ekaramad@chromium.org>
> Commit-Queue: Kevin McNee <mcnee@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#582240}

TBR=ekaramad@chromium.org,mcnee@chromium.org

Change-Id: I6c84e6950d7f74ae5b15eec084a536115e635ceb
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 147644
Reviewed-on: https://chromium-review.googlesource.com/1172002Reviewed-by: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582429}

chrome/browser/apps/guest_view/web_view_interactive_browsertest.cc

@@ -871,6 +871,14 @@ IN_PROC_BROWSER_TEST_F(WebViewFocusInteractiveTest, Focus_AdvanceFocus) {
     // move the focus to the next focusable element.
     ExtensionTestMessageListener listener("button1-advance-focus", false);
     listener.set_failure_message("TEST_FAILED");
+    // TODO(fsamuel): A third Tab key press should not be necessary.
+    // The <webview> will take keyboard focus but it will not focus an initial
+    // element. The initial element is dependent upon tab direction which blink
+    // does not propagate to the plugin.
+    // See http://crbug.com/147644.
+    content::SimulateKeyPress(embedder_web_contents, ui::DomKey::TAB,
+                              ui::DomCode::TAB, ui::VKEY_TAB, false, false,
+                              false, false);
     content::SimulateKeyPress(embedder_web_contents, ui::DomKey::TAB,
                               ui::DomCode::TAB, ui::VKEY_TAB, false, false,
                               false, false);