Prevent BottomSheet from receiving multiple onShowContextualSearch events

Contextual Search show/hide events are not 1:1. Show can be called
multiple times when the text selection changes (which is pretty
often). This would cause the bottom sheet to remain hidden after
Contextual Search was gone.

This patch checks if Contextual Search is already showing in the
BottomSheetController as not to change the behavior of other
Contextual Search observers.

Bug: 827353
Change-Id: Ib133224042cef6509d3cd7b81df78810093190f8
Reviewed-on: https://chromium-review.googlesource.com/1012193Reviewed-by: Theresa <twellington@chromium.org>
Commit-Queue: Matthew Jones <mdjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550689}

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

@@ -170,6 +170,8 @@ public class BottomSheetController implements ApplicationStatus.ActivityStateLis
                 @Override
                 public void onShowContextualSearch(
                         @Nullable GSAContextDisplaySelection selectionContext) {
+                    // Contextual Search can call this method more than once per show event.
+                    if (mIsCompositedUIShowing) return;
                     mWasSheetShowing = mBottomSheet.getSheetState() == BottomSheet.SHEET_STATE_PEEK;
                     mIsCompositedUIShowing = true;
                     mBottomSheet.setSheetState(BottomSheet.SHEET_STATE_HIDDEN, false,