PreviewTab: Make sure the hidden preview tab visible on show request

It is possible that the preview tab is requested to open, while it
is already the current bottom sheet content just hidden in the
controller. This CL makes sure it will be visible by moving it to
the appropriate peek/open state.

Bug: 1057966
Change-Id: Id3dca309738d22cca5086325272a4aa0dff67724
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2087307Reviewed-by: Matthew Jones <mdjones@chromium.org>
Commit-Queue: Jinsuk Kim <jinsukkim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#748479}

chrome/android/java/src/org/chromium/chrome/browser/widget/bottomsheet/BottomSheetController.java

@@ -556,7 +556,12 @@ public class BottomSheetController implements Destroyable {
         if (mBottomSheet == null) mSheetInitializer.run();
 
         // If already showing the requested content, do nothing.
-        if (content == mBottomSheet.getCurrentSheetContent()) return true;
+        if (content == mBottomSheet.getCurrentSheetContent()) {
+            if (getSheetState() == SheetState.HIDDEN) {
+                mBottomSheet.setSheetState(mBottomSheet.getOpeningState(), animate);
+            }
+            return true;
+        }
 
         // Showing the sheet requires a tab.
         if (mTabProvider.get() == null) return false;