[EoC] Speculative crash fix for showing suggestions after destruction

This adds a speculative fix for a crash reported when tapping both the
EoC toolbar button and clear tab button at the same time. This CL
ignores clicks on the toolbar button if the model is not prepared (e.g.
has been cleared before the click handler is invoked) and adds a
null check before showing content.

BUG=873052

Change-Id: I073919ce38f73046d9644523135d5b6cdbd42c59
Reviewed-on: https://chromium-review.googlesource.com/1172940
Commit-Queue: Theresa <twellington@chromium.org>
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582684}

chrome/android/java/src/org/chromium/chrome/browser/contextual_suggestions/ContextualSuggestionsCoordinator.java

@@ -105,6 +105,13 @@ public class ContextualSuggestionsCoordinator {
      *                          things needed to display suggestions (e.g. favicons, thumbnails).
      */
     void showSuggestions(ContextualSuggestionsSource suggestionsSource) {
+        // If the content coordinator has already been destroyed when this method is called, return
+        // early. See https://crbug.com/873052.
+        if (mContentCoordinator == null) {
+            assert false : "ContentCoordinator false when #showSuggestions was called.";
+            return;
+        }
+
         SuggestionsNavigationDelegate navigationDelegate = new SuggestionsNavigationDelegateImpl(
                 mActivity, mProfile, mBottomSheetController.getBottomSheet(), mTabModelSelector);
         SuggestionsUiDelegateImpl uiDelegate = new SuggestionsUiDelegateImpl(suggestionsSource,

chrome/android/java/src/org/chromium/chrome/browser/contextual_suggestions/ContextualSuggestionsMediator.java

@@ -73,6 +73,7 @@ class ContextualSuggestionsMediator
     private @Nullable TextBubble mHelpBubble;
     private @Nullable WebContents mCurrentWebContents;
 
+    private boolean mModelPreparedForCurrentTab;
     private boolean mSuggestionsSetOnBottomSheet;
     private boolean mDidSuggestionsShowForTab;
     private boolean mHasRecordedPeekEventForTab;
@@ -279,7 +280,7 @@ class ContextualSuggestionsMediator
     }
 
     private void onToolbarButtonClicked() {
-        if (mSuggestionsSetOnBottomSheet) return;
+        if (mSuggestionsSetOnBottomSheet || !mModelPreparedForCurrentTab) return;
 
         maybeShowContentInSheet();
         mCoordinator.showSuggestions(mSuggestionsSource);
@@ -395,7 +396,7 @@ class ContextualSuggestionsMediator
      * be cleared.
      */
     private void clearSuggestions() {
-        // TODO(twellington): Does this signal need to go back to FetchHelper?
+        mModelPreparedForCurrentTab = false;
 
         // Remove suggestions before clearing model state so that views don't respond to model
         // changes while suggestions are hiding. See https://crbug.com/840579.
@@ -470,6 +471,8 @@ class ContextualSuggestionsMediator
         mModel.setMenuButtonDelegate(this);
         mModel.setDefaultToolbarClickListener(view -> mCoordinator.expandBottomSheet());
         mModel.setTitle(title);
+
+        mModelPreparedForCurrentTab = true;
     }
 
     private void maybeShowContentInSheet() {