Add a null check in LayoutManagerChromePhone#tabCreating.

Allow active layout to be null in LayoutManagerChromePhone#tabCreating.

Bug: 1140406
Change-Id: Ic4104a29689892bbe9101ad3f7d3b4d4018aaece
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2527684Reviewed-by: Xi Han <hanxi@chromium.org>
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Commit-Queue: Hao Dong <spdonghao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#825871}

chrome/android/java/src/org/chromium/chrome/browser/compositor/layouts/LayoutManagerChromePhone.java

@@ -135,8 +135,8 @@ public class LayoutManagerChromePhone extends LayoutManagerChrome {
 
     @Override
     protected void tabCreating(int sourceId, String url, boolean isIncognito) {
-        if (!getActiveLayout().isStartingToHide() && overlaysHandleTabCreating()
-                && getActiveLayout().handlesTabCreating()) {
+        if (getActiveLayout() != null && !getActiveLayout().isStartingToHide()
+                && overlaysHandleTabCreating() && getActiveLayout().handlesTabCreating()) {
             // If the current layout in the foreground, let it handle the tab creation animation.
             // This check allows us to switch from the StackLayout to the SimpleAnimationLayout
             // smoothly.
@@ -151,7 +151,9 @@ public class LayoutManagerChromePhone extends LayoutManagerChrome {
                     startShowing(mSimpleAnimationLayout, false);
                 }
             }
-            getActiveLayout().onTabCreating(sourceId);
+            if (getActiveLayout() != null) {
+                getActiveLayout().onTabCreating(sourceId);
+            }
         }
     }