[Chrome Home] Fix incorrect toolbar showing when multiple buttons clicked

Set tab stack button to not clickable if new tab bottom sheet is on
show. This will prevent tab stack button being clicked after new tab
button is clicked that changes the toolbar to tab switcher mode.

Bug: 747785
Change-Id: Ie7df8acc034bf9dcb3330dd1e235030b561f3060
Reviewed-on: https://chromium-review.googlesource.com/695867
Commit-Queue: Becky Zhou <huayinz@chromium.org>
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#505889}

chrome/android/java/src/org/chromium/chrome/browser/toolbar/BottomToolbarPhone.java

@@ -750,6 +750,8 @@ public class BottomToolbarPhone extends ToolbarPhone {
             updateMenuButtonClickableState();
         }
 
+        mToggleTabStackButton.setClickable(mBottomSheet == null || !mBottomSheet.isShowingNewTab());
+
         DrawableCompat.setTint(mLocationBarBackground,
                 isIncognito() ? Color.WHITE
                               : ApiCompatibilityUtils.getColor(