The Java Client should be aware of the readback status.

content/public/android/java/src/org/chromium/content/browser/ContentReadbackHandler.java

Index: content/public/android/java/src/org/chromium/content/browser/ContentReadbackHandler.java
diff --git a/content/public/android/java/src/org/chromium/content/browser/ContentReadbackHandler.java b/content/public/android/java/src/org/chromium/content/browser/ContentReadbackHandler.java
index ded0664c6296157b5f02f2260aacb8c15a4f64f0..1d288697fdc5c8d53642ba24bf399d1b05b76c62 100644
--- a/content/public/android/java/src/org/chromium/content/browser/ContentReadbackHandler.java
+++ b/content/public/android/java/src/org/chromium/content/browser/ContentReadbackHandler.java
@@ -11,6 +11,7 @@ import android.util.SparseArray;
 import org.chromium.base.CalledByNative;
 import org.chromium.base.JNINamespace;
 import org.chromium.base.ThreadUtils;
+import org.chromium.content_public.browser.readback_types.ReadbackResponse;
 import org.chromium.ui.base.WindowAndroid;
 
 /**
@@ -27,7 +28,7 @@ public abstract class ContentReadbackHandler {
          * @param bitmap     The {@link Bitmap} of the content.  Null will be passed for readback
          *                   failure.
          */
-        public void onFinishGetBitmap(Bitmap bitmap);
+        public void onFinishGetBitmap(Bitmap bitmap, int response);
     }
 
     private int mNextReadbackId = 1;
@@ -59,11 +60,11 @@ public abstract class ContentReadbackHandler {
 
 
     @CalledByNative
-    private void notifyGetBitmapFinished(int readbackId, Bitmap bitmap) {
+    private void notifyGetBitmapFinished(int readbackId, Bitmap bitmap, int response) {
         GetBitmapCallback callback = mGetBitmapRequests.get(readbackId);
         if (callback != null) {
             mGetBitmapRequests.delete(readbackId);
-            callback.onFinishGetBitmap(bitmap);
+            callback.onFinishGetBitmap(bitmap, response);
         } else {
             // readback Id is unregistered.
             assert false : "Readback finished for unregistered Id: " + readbackId;
@@ -83,7 +84,7 @@ public abstract class ContentReadbackHandler {
     public void getContentBitmapAsync(float scale, Rect srcRect, ContentViewCore view,
             GetBitmapCallback callback) {
         if (!readyForReadback()) {
-            callback.onFinishGetBitmap(null);
+            callback.onFinishGetBitmap(null, ReadbackResponse.SURFACE_UNAVAILABLE);
             return;
         }
         ThreadUtils.assertOnUiThread();
@@ -103,7 +104,7 @@ public abstract class ContentReadbackHandler {
      */
     public void getCompositorBitmapAsync(WindowAndroid windowAndroid, GetBitmapCallback callback) {
         if (!readyForReadback()) {
-            callback.onFinishGetBitmap(null);
+            callback.onFinishGetBitmap(null, ReadbackResponse.SURFACE_UNAVAILABLE);
             return;
         }
         ThreadUtils.assertOnUiThread();