Use ObserverList for OverviewModeBehavior

This switches to use ObserverList
OverviewModeObservers in ChromeTabbedActivity. This list gets frequently
modified during iteration, and Array List is throwing a
ConcurrentModificationException because of this right now.

BUG=938236
TBR=yusufo@google.com

(cherry picked from commit 0775dc30ab0ccfd38181c219c3bc725ae03a5fa4)

Change-Id: I65c99b774ae34f2984ddb8f5ca254ff8e2af4569
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1515713
Commit-Queue: Yusuf Ozuysal <yusufo@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#639660}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1518364
Reviewed-by: Yusuf Ozuysal <yusufo@chromium.org>
Cr-Commit-Position: refs/branch-heads/3729@{#63}
Cr-Branched-From: d4a8972-refs/heads/master@{#638880}

Author: Yusuf Ozuysal

chrome/android/features/tab_ui/java/src/org/chromium/chrome/browser/tasks/tab_management/GridTabSwitcherMediator.java

@@ -12,6 +12,7 @@
 import static org.chromium.chrome.browser.tasks.tab_management.TabListContainerProperties.TOP_CONTROLS_HEIGHT;
 import static org.chromium.chrome.browser.tasks.tab_management.TabListContainerProperties.VISIBILITY_LISTENER;
 
+import org.chromium.base.ObserverList;
 import org.chromium.chrome.browser.compositor.layouts.OverviewModeController;
 import org.chromium.chrome.browser.fullscreen.ChromeFullscreenManager;
 import org.chromium.chrome.browser.fullscreen.FullscreenManager;
@@ -24,9 +25,6 @@
 import org.chromium.chrome.browser.tabmodel.TabSelectionType;
 import org.chromium.ui.modelutil.PropertyModel;
 
-import java.util.ArrayList;
-import java.util.List;
-
 /**
  * The Mediator that is responsible for resetting the tab grid based on visibility and model
  * changes.
@@ -42,7 +40,7 @@ class GridTabSwitcherMediator
     private final TabModelSelector mTabModelSelector;
     private final TabModelSelectorTabModelObserver mTabModelObserver;
     private final TabModelSelectorObserver mTabModelSelectorObserver;
-    private final List<OverviewModeObserver> mObservers = new ArrayList<>();
+    private final ObserverList<OverviewModeObserver> mObservers = new ObserverList<>();
     private final ChromeFullscreenManager mFullscreenManager;
     private final ChromeFullscreenManager.FullscreenListener mFullscreenListener =
             new ChromeFullscreenManager.FullscreenListener() {
@@ -138,13 +136,13 @@ public boolean overviewVisible() {
     }
 
     @Override
-    public void addOverviewModeObserver(OverviewModeObserver listener) {
-        mObservers.add(listener);
+    public void addOverviewModeObserver(OverviewModeObserver observer) {
+        mObservers.addObserver(observer);
     }
 
     @Override
-    public void removeOverviewModeObserver(OverviewModeObserver listener) {
-        mObservers.remove(listener);
+    public void removeOverviewModeObserver(OverviewModeObserver observer) {
+        mObservers.removeObserver(observer);
     }
 
     @Override

chrome/android/java/src/org/chromium/chrome/browser/ChromeTabbedActivity.java

@@ -42,6 +42,7 @@
 import org.chromium.base.ContextUtils;
 import org.chromium.base.Log;
 import org.chromium.base.MemoryPressureListener;
+import org.chromium.base.ObserverList;
 import org.chromium.base.ThreadUtils;
 import org.chromium.base.TraceEvent;
 import org.chromium.base.VisibleForTesting;
@@ -170,7 +171,6 @@
 
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
-import java.util.ArrayList;
 import java.util.List;
 import java.util.Locale;
 
@@ -333,7 +333,7 @@ public void closeAllIncognitoTabs() {
     private static class OverviewModeControllerContainer
             implements OverviewModeObserver, OverviewModeController {
         private OverviewModeController mInternalOverviewModeController;
-        private List<OverviewModeObserver> mOverviewModeObserverList = new ArrayList<>();
+        private ObserverList<OverviewModeObserver> mOverviewModeObserverList = new ObserverList<>();
 
         @Override
         public boolean overviewVisible() {
@@ -342,25 +342,27 @@ public boolean overviewVisible() {
         }
 
         @Override
-        public void addOverviewModeObserver(OverviewModeObserver listener) {
-            mOverviewModeObserverList.add(listener);
+        public void addOverviewModeObserver(OverviewModeObserver observer) {
+            mOverviewModeObserverList.addObserver(observer);
         }
 
         @Override
-        public void removeOverviewModeObserver(OverviewModeObserver listener) {
-            mOverviewModeObserverList.remove(listener);
+        public void removeOverviewModeObserver(OverviewModeObserver observer) {
+            mOverviewModeObserverList.removeObserver(observer);
         }
 
         @Override
         public void hideOverview(boolean animate) {
-            if (mInternalOverviewModeController != null)
+            if (mInternalOverviewModeController != null) {
                 mInternalOverviewModeController.hideOverview(animate);
+            }
         }
 
         @Override
         public void showOverview(boolean animate) {
-            if (mInternalOverviewModeController != null)
+            if (mInternalOverviewModeController != null) {
                 mInternalOverviewModeController.showOverview(animate);
+            }
         }
 
         @Override