aw: Make repeated detachGLFunctor work

detachGLFunctor is called every time the webview is detached (ie when
hardware acceleration is torn down and cleaned up). This can happen many
times since webview can be attached and detached many times.

However the implementation in the glue layer only does something on the
first call.

Also in general, it's a bad pattern for CleanupReference to have strong
java refs.

It's not necessary to call detachGLFunctor on gc; detach is enough. So
move all that code out of the DestroyRunnable of the CleanupReference.

This is a long standing bug since the first release of chromium webview.

BUG=

Review URL: https://codereview.chromium.org/872403006

Cr-Commit-Position: refs/heads/master@{#315051}

android_webview/glue/java/src/com/android/webview/chromium/DrawGLFunctor.java

@@ -24,10 +24,13 @@ class DrawGLFunctor {
     // Pointer to native side instance
     private CleanupReference mCleanupReference;
     private DestroyRunnable mDestroyRunnable;
+    private final long mNativeDrawGLFunctor;
     private WebViewDelegate mWebViewDelegate;
+    View mContainerView;
 
     public DrawGLFunctor(long viewContext, WebViewDelegate webViewDelegate) {
-        mDestroyRunnable = new DestroyRunnable(nativeCreateGLFunctor(viewContext), webViewDelegate);
+        mNativeDrawGLFunctor = nativeCreateGLFunctor(viewContext);
+        mDestroyRunnable = new DestroyRunnable(mNativeDrawGLFunctor);
         mCleanupReference = new CleanupReference(this, mDestroyRunnable);
         mWebViewDelegate = webViewDelegate;
     }
@@ -39,11 +42,14 @@ class DrawGLFunctor {
             mCleanupReference = null;
             mDestroyRunnable = null;
             mWebViewDelegate = null;
+            mContainerView = null;
         }
     }
 
     public void detach() {
-        mDestroyRunnable.detachNativeFunctor();
+        if (mWebViewDelegate != null && mContainerView != null) {
+            mWebViewDelegate.detachDrawGlFunctor(mContainerView, mNativeDrawGLFunctor);
+        }
     }
 
     public boolean requestDrawGL(Canvas canvas, View containerView, boolean waitForCompletion) {
@@ -60,7 +66,7 @@ class DrawGLFunctor {
             return false;
         }
 
-        mDestroyRunnable.mContainerView = containerView;
+        mContainerView = containerView;
 
         if (canvas == null) {
             mWebViewDelegate.invokeDrawGlFunctor(
@@ -80,29 +86,19 @@ class DrawGLFunctor {
     // IMPORTANT: this class must not hold any reference back to the outer DrawGLFunctor
     // instance, as that will defeat GC of that object.
     private static final class DestroyRunnable implements Runnable {
-        private WebViewDelegate mWebViewDelegate;
-        View mContainerView;
-        long mNativeDrawGLFunctor;
-        DestroyRunnable(long nativeDrawGLFunctor, WebViewDelegate webViewDelegate) {
+        private long mNativeDrawGLFunctor;
+        DestroyRunnable(long nativeDrawGLFunctor) {
             mNativeDrawGLFunctor = nativeDrawGLFunctor;
-            mWebViewDelegate = webViewDelegate;
+            assert mNativeDrawGLFunctor != 0;
         }
 
         // Called when the outer DrawGLFunctor instance has been GC'ed, i.e this is its finalizer.
         @Override
         public void run() {
-            detachNativeFunctor();
+            assert mNativeDrawGLFunctor != 0;
             nativeDestroyGLFunctor(mNativeDrawGLFunctor);
             mNativeDrawGLFunctor = 0;
         }
-
-        void detachNativeFunctor() {
-            if (mNativeDrawGLFunctor != 0 && mContainerView != null && mWebViewDelegate != null) {
-                mWebViewDelegate.detachDrawGlFunctor(mContainerView, mNativeDrawGLFunctor);
-            }
-            mContainerView = null;
-            mWebViewDelegate = null;
-        }
     }
 
     private static native long nativeCreateGLFunctor(long viewContext);