Import polymer in a single place and remove d3 hacks

tracing/trace_viewer.gypi

 # Copyright (c) 2015 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.
 
 {
   'variables': {
     'tracing_css_files': [
       'tracing/ui/base/line_chart.css',
       'tracing/ui/base/list_view.css',
       'tracing/ui/base/pie_chart.css',
@@ skipping 338 matching lines @@
       'tracing/ui/base/info_bar.html',
       'tracing/ui/base/info_bar_group.html',
       'tracing/ui/base/line_chart.html',
       'tracing/ui/base/list_view.html',
       'tracing/ui/base/mouse_mode_icon.html',
       'tracing/ui/base/mouse_mode_selector.html',
       'tracing/ui/base/mouse_modes.html',
       'tracing/ui/base/mouse_tracker.html',
       'tracing/ui/base/overlay.html',
       'tracing/ui/base/pie_chart.html',
+      'tracing/ui/base/polymer_postload.html',
+      'tracing/ui/base/polymer_preload.html',
       'tracing/ui/base/quad_stack_view.html',
       'tracing/ui/base/tab_view.html',
       'tracing/ui/base/table.html',
       'tracing/ui/base/timing_tool.html',
       'tracing/ui/base/toolbar_button.html',
       'tracing/ui/base/ui.html',
       'tracing/ui/base/ui_state.html',
       'tracing/ui/base/utils.html',
-      'tracing/ui/base/webcomponents.html',
       'tracing/ui/brushing_state.html',
       'tracing/ui/brushing_state_controller.html',
       'tracing/ui/extras/about_tracing/about_tracing.html',
       'tracing/ui/extras/about_tracing/inspector_connection.html',
       'tracing/ui/extras/about_tracing/inspector_tracing_controller_client.html',
       'tracing/ui/extras/about_tracing/profiling_view.html',
       'tracing/ui/extras/about_tracing/record_controller.html',
       'tracing/ui/extras/about_tracing/record_selection_dialog.html',
       'tracing/ui/extras/about_tracing/tracing_controller_client.html',
       'tracing/ui/extras/about_tracing/xhr_based_tracing_controller_client.html',
@@ skipping 131 matching lines @@
       'tracing/ui/images/chrome-right.png',
       'tracing/ui/images/ui-states.png',
     ],
     'tracing_files': [
       '<@(tracing_css_files)',
       '<@(tracing_js_html_files)',
       '<@(tracing_img_files)',
     ],
   }
 }