Android: Fix the hidden bottom sheet when omnibox is off-screen

Adjusts the offset of the bottom sheet so that it appears as expected
when the omnibox control is not on screen. This CL fixes the issue
by overriding BottomSheetContent.onHideScroll so the browser controls
won't have an effect on NavigationSHeet.

Bug: 996535
Change-Id: I32d5a1a15d5a7275ce0fdba1a86e7dd82a570086
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1767283Reviewed-by: Matthew Jones <mdjones@chromium.org>
Commit-Queue: Jinsuk Kim <jinsukkim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#690933}

chrome/android/java/src/org/chromium/chrome/browser/gesturenav/NavigationSheetCoordinator.java

@@ -283,6 +283,11 @@ class NavigationSheetCoordinator implements BottomSheetContent, NavigationSheet
         return true;
     }
 
+    @Override
+    public boolean hideOnScroll() {
+        return false;
+    }
+
     @Override
     public int getSheetContentDescriptionStringId() {
         return R.string.overscroll_navigation_sheet_description;