[Offline indicator v2] Fix wrong toolbar offset when swiping new tab

This CL fixes a bug where if the user swipes the toolbar immediately
after opening a new tab (easily reproducible w/ context menu > open in
incognito tab), top controls have the wrong offset and get hidden.

This is caused by ChromeFullscreenManager#onInteractabilityChanged()
which pushes offsets from TabBrowserControlsOffsetHelper even if the
offsets aren't initialized.

This is fixed by adding a simple check and returning early if the
offsets aren't initialized.

Bug: 1048596
Change-Id: I3db087db835f81067018f808ee03974fb4d1adc8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2042677Reviewed-by: Theresa  <twellington@chromium.org>
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Commit-Queue: Sinan Sahin <sinansahin@google.com>
Cr-Commit-Position: refs/heads/master@{#739202}

chrome/android/java/src/org/chromium/chrome/browser/fullscreen/ChromeFullscreenManager.java

@@ -310,6 +310,8 @@ public class ChromeFullscreenManager extends FullscreenManager
 
                 TabBrowserControlsOffsetHelper offsetHelper =
                         TabBrowserControlsOffsetHelper.get(currentTab);
+                if (!offsetHelper.offsetInitialized()) return;
+
                 onOffsetsChanged(offsetHelper.topControlsOffset(),
                         offsetHelper.bottomControlsOffset(), offsetHelper.contentOffset(),
                         offsetHelper.topControlsMinHeightOffset(),