The Java Client should be aware of the readback status.

content/public/android/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/config.gni")
 import("//build/config/android/rules.gni")
 
 content_jni_gypi_values = exec_script("//build/gypi_to_gn.py",
                                       [ rebase_path("../../content_jni.gypi") ],
                                       "scope",
@@ skipping 93 matching lines @@
     "values-zh-rTW/android_content_strings.xml",
   ]
 }
 
 java_cpp_enum("content_public_android_java_enums_srcjar") {
   sources = [
     "//content/browser/android/content_view_core_impl.cc",
     "//content/browser/android/gesture_event_type.h",
     "//content/browser/gamepad/gamepad_standard_mappings.h",
     "//content/public/browser/navigation_controller.h",
+    "//content/public/browser/readback_types.h",
     "//content/public/common/console_message_level.h",
     "//content/public/common/result_codes.h",
     "//content/public/common/screen_orientation_values.h",
     "//content/public/common/speech_recognition_error.h",
     "//content/public/common/top_controls_state.h",
   ]
   outputs = [
     "org/chromium/content/browser/GestureEventType.java",
     "org/chromium/content/browser/input/CanonicalAxisIndex.java",
     "org/chromium/content/browser/input/CanonicalButtonIndex.java",
     "org/chromium/content/browser/input/PopupItemType.java",
     "org/chromium/content_public/browser/navigation_controller/LoadURLType.java",
     "org/chromium/content_public/browser/navigation_controller/UserAgentOverrideOption.java",
+    "org/chromium/content_public/browser/readback_types/ReadbackResponse.java",
     "org/chromium/content_public/common/ConsoleMessageLevel.java",
     "org/chromium/content_public/common/ResultCode.java",
     "org/chromium/content_public/common/ScreenOrientationValues.java",
     "org/chromium/content_public/common/SpeechRecognitionErrorCode.java",
     "org/chromium/content_public/common/TopControlsState.java",
   ]
 }
 
 generate_jar_jni("jar_jni") {
   jni_package = "content"
@@ skipping 32 matching lines @@
     "//third_party/mojo/src/mojo/public/interfaces/bindings/tests:test_interfaces_java",
     "//third_party/mojo/src/mojo/public/java:bindings",
     "//third_party/mojo/src/mojo/public/java:system",
     "//ui/android:ui_java",
     ":content_java",
   ]
 
   DEPRECATED_java_in_dir = "javatests/src"
 }
 # TODO(GYP): content_icudata