Revert "Use ObserverList for OverviewModeBehavior"

This reverts commit 7dcbfa1.

Reason for revert: breaks build, bug 941226

Original change's description:
> 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
> [email protected]
> 
> (cherry picked from commit 0775dc30ab0ccfd38181c219c3bc725ae03a5fa4)
> 
> Change-Id: I65c99b774ae34f2984ddb8f5ca254ff8e2af4569
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1515713
> Commit-Queue: Yusuf Ozuysal <[email protected]>
> Reviewed-by: Ted Choc <[email protected]>
> Cr-Original-Commit-Position: refs/heads/master@{#639660}
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1518364
> Reviewed-by: Yusuf Ozuysal <[email protected]>
> Cr-Commit-Position: refs/branch-heads/3729@{#63}
> Cr-Branched-From: d4a8972-refs/heads/master@{#638880}

[email protected],[email protected]

Change-Id: I20a905b15643de0cc270a5c91dcf79f4a81d9c6d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 938236
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1519449
Reviewed-by: Krishna Govind <[email protected]>
Cr-Commit-Position: refs/branch-heads/3729@{#70}
Cr-Branched-From: d4a8972-refs/heads/master@{#638880}

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

@@ -12,7 +12,6 @@
 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;
@@ -25,6 +24,9 @@
 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.
@@ -40,7 +42,7 @@ class GridTabSwitcherMediator
     private final TabModelSelector mTabModelSelector;
     private final TabModelSelectorTabModelObserver mTabModelObserver;
     private final TabModelSelectorObserver mTabModelSelectorObserver;
-    private final ObserverList<OverviewModeObserver> mObservers = new ObserverList<>();
+    private final List<OverviewModeObserver> mObservers = new ArrayList<>();
     private final ChromeFullscreenManager mFullscreenManager;
     private final ChromeFullscreenManager.FullscreenListener mFullscreenListener =
             new ChromeFullscreenManager.FullscreenListener() {
@@ -136,13 +138,13 @@ public boolean overviewVisible() {
     }
 
     @Override
-    public void addOverviewModeObserver(OverviewModeObserver observer) {
-        mObservers.addObserver(observer);
+    public void addOverviewModeObserver(OverviewModeObserver listener) {
+        mObservers.add(listener);
     }
 
     @Override
-    public void removeOverviewModeObserver(OverviewModeObserver observer) {
-        mObservers.removeObserver(observer);
+    public void removeOverviewModeObserver(OverviewModeObserver listener) {
+        mObservers.remove(listener);
     }
 
     @Override

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

@@ -42,7 +42,6 @@
 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;
@@ -171,6 +170,7 @@
 
 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 ObserverList<OverviewModeObserver> mOverviewModeObserverList = new ObserverList<>();
+        private List<OverviewModeObserver> mOverviewModeObserverList = new ArrayList<>();
 
         @Override
         public boolean overviewVisible() {
@@ -342,27 +342,25 @@ public boolean overviewVisible() {
         }
 
         @Override
-        public void addOverviewModeObserver(OverviewModeObserver observer) {
-            mOverviewModeObserverList.addObserver(observer);
+        public void addOverviewModeObserver(OverviewModeObserver listener) {
+            mOverviewModeObserverList.add(listener);
         }
 
         @Override
-        public void removeOverviewModeObserver(OverviewModeObserver observer) {
-            mOverviewModeObserverList.removeObserver(observer);
+        public void removeOverviewModeObserver(OverviewModeObserver listener) {
+            mOverviewModeObserverList.remove(listener);
         }
 
         @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