Support dragging texts into Android WebView.

ui/base/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/compiler/compiler.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 
 if (is_android) {
@@ skipping 552 matching lines @@
   if (is_android) {
     deps += [
       ":ui_base_jni_headers",
       "//ui/android:ui_java",
     ]
 
     libs += [ "jnigraphics" ]
   }
 
   if (is_android && !use_aura) {
+    sources += [
+      "dragdrop/drag_drop_types.h",
+      "dragdrop/drop_target_event.cc",
+      "dragdrop/drop_target_event.h",
+      "dragdrop/os_exchange_data.cc",
+      "dragdrop/os_exchange_data.h",
+      "dragdrop/os_exchange_data_provider_android.cc",
+      "dragdrop/os_exchange_data_provider_android.h",
+    ]
+
     sources -= [
       "cursor/cursor_android.cc",
       "cursor/image_cursors.cc",
       "cursor/image_cursors.h",
       "default_theme_provider.cc",
       "dragdrop/drag_utils.cc",
       "dragdrop/drag_utils.h",
       "idle/idle.cc",
       "idle/idle.h",
       "idle/idle_android.cc",
@@ skipping 329 matching lines @@
   }
   if (is_mac) {
     data += [ "$root_out_dir/ui_unittests Framework.framework/" ]
 
     if (is_asan && symbol_level == 0) {
       data += [ "$root_out_dir/ui_base_unittests.dSYM/" ]
     }
   }
 }
 # TODO(GYP) Mac (ui_base_tests_bundle)