Revert of aw: Ensure WebView stays alive until functor detach

android_webview/java/src/org/chromium/android_webview/AwContents.java

Index: android_webview/java/src/org/chromium/android_webview/AwContents.java
diff --git a/android_webview/java/src/org/chromium/android_webview/AwContents.java b/android_webview/java/src/org/chromium/android_webview/AwContents.java
index 903c00aa4325a262a00ef65d24a9288d6734134d..6c350aef581da8f80188af28408a39719a3ccc7d 100644
--- a/android_webview/java/src/org/chromium/android_webview/AwContents.java
+++ b/android_webview/java/src/org/chromium/android_webview/AwContents.java
@@ -80,10 +80,8 @@
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.util.HashMap;
-import java.util.HashSet;
 import java.util.Locale;
 import java.util.Map;
-import java.util.Set;
 import java.util.concurrent.Callable;
 
 /**
@@ -257,11 +255,6 @@
     private final boolean mSupportsFunctorDetachedCallback;
     private boolean mFunctorDetachedCallbackPending;
 
-    // TODO(boliu): This is temporary for M51. AwContents is in |sGcRoots| if and only if
-    // mFunctorDetachedCallbackPending is true, to ensure that the whole system do not
-    // get garbage collected before functor detached callback.
-    private static final Set<AwContents> sGcRoots = new HashSet<>();
-
     private boolean mIsPaused;
     private boolean mIsViewVisible;
     private boolean mIsWindowVisible;
@@ -2355,7 +2348,6 @@
     // FullScreenView.
     public void onFunctorDetached() {
         mFunctorDetachedCallbackPending = false;
-        sGcRoots.remove(this);
         if (isDestroyed(NO_WARN) && mAwGLFunctor != null) {
             mAwGLFunctor.destroy();
             mAwGLFunctor = null;
@@ -2959,9 +2951,6 @@
                 did_draw = mNativeGLDelegate.requestDrawGL(canvas, false, mContainerView);
                 mFunctorDetachedCallbackPending |=
                         (mSupportsFunctorDetachedCallback && did_draw && !isFullScreen());
-                if (mFunctorDetachedCallbackPending) {
-                    sGcRoots.add(AwContents.this);
-                }
             }
             if (did_draw) {
                 int scrollXDiff = mContainerView.getScrollX() - scrollX;