cc: Delete unused DisplayItem::GetPicture func

cc/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/ui.gni")
 import("//cc/cc.gni")
 
 cc_component("cc") {
   sources = [
     "debug/benchmark_instrumentation.cc",
@@ skipping 232 matching lines @@
     "playback/clip_display_item.cc",
     "playback/clip_display_item.h",
     "playback/clip_path_display_item.cc",
     "playback/clip_path_display_item.h",
     "playback/compositing_display_item.cc",
     "playback/compositing_display_item.h",
     "playback/decoded_draw_image.cc",
     "playback/decoded_draw_image.h",
     "playback/discardable_image_map.cc",
     "playback/discardable_image_map.h",
-    "playback/display_item.cc",
     "playback/display_item.h",
     "playback/display_item_list.cc",
     "playback/display_item_list.h",
     "playback/draw_image.cc",
     "playback/draw_image.h",
     "playback/drawing_display_item.cc",
     "playback/drawing_display_item.h",
     "playback/filter_display_item.cc",
     "playback/filter_display_item.h",
     "playback/float_clip_display_item.cc",
@@ skipping 724 matching lines @@
   data = [
     "test/data/",
 
     # Needed for isolate script to execute.
     "//testing/scripts/common.py",
     "//testing/xvfb.py",
     "//testing/scripts/run_gtest_perf_test.py",
     "//tools/perf/generate_legacy_perf_dashboard_json.py",
   ]
 }