Exit fullscreen when tab modal dialog is about to show

Exiting fullscreen on tab modal dialog shown could prevent it not being
shown inside fullscreen mode, and also provides a better escape path
for the user who doesn't want to interact with the dialog.

Bug: 958742
Change-Id: I831a77016e94b6797aae04e425e4a6aae8a3eb30
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1603982Reviewed-by: Ted Choc <tedchoc@chromium.org>
Commit-Queue: Becky Zhou <huayinz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#658413}

chrome/android/java/src/org/chromium/chrome/browser/modaldialog/TabModalPresenter.java

@@ -353,6 +353,9 @@ public class TabModalPresenter
     private void onTabModalDialogStateChanged(boolean isShowing) {
         TabAttributes.from(mActiveTab).set(TabAttributeKeys.MODAL_DIALOG_SHOWING, isShowing);
 
+        // Make sure to exit fullscreen mode before showing the tab modal dialog view.
+        if (isShowing) mActiveTab.exitFullscreenMode();
+
         // Also need to update browser control state after dismissal to refresh the constraints.
         TabBrowserControlsOffsetHelper offsetHelper = getControlsOffsetHelper();
         if (isShowing && mActiveTab.areRendererInputEventsIgnored()) {