Delete blink::WebGraphicsContext3D and cc_blink::ContextProviderWebContext

cc/blink/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("//testing/test.gni")
 
 # GYP version: //cc/blink/cc_blink.gyp:cc_blink
 component("blink") {
   output_name = "cc_blink"
 
   sources = [
     "cc_blink_export.h",
-    "context_provider_web_context.h",
     "scrollbar_impl.cc",
     "scrollbar_impl.h",
     "web_compositor_support_impl.cc",
     "web_compositor_support_impl.h",
     "web_content_layer_impl.cc",
     "web_content_layer_impl.h",
     "web_display_item_list_impl.cc",
     "web_display_item_list_impl.h",
     "web_external_bitmap_impl.cc",
     "web_external_bitmap_impl.h",
@@ skipping 46 matching lines @@
       "//cc:test_support",
       "//skia",
       "//testing/gmock",
       "//testing/gtest",
       "//third_party/WebKit/public:blink_for_unittests",
       "//ui/gfx:test_support",
       "//ui/gfx/geometry",
     ]
   }
 }