Remove old *_scroll_200_layer_grid rendering stories.

These stories are superceded by newer stories such as
infinite_scroll_root_n_layers_99 and css_opacity_plus_n_layers_99.

Now that we have had overlapping data from the new stories for some
time, the old stories can be removed.

BUG=878951

Change-Id: Idb146ed7d9f5420bac1d5217e86c6547a772efe5
Reviewed-on: https://chromium-review.googlesource.com/c/1334929
Commit-Queue: Victor Miura <vmiura@chromium.org>
Reviewed-by: Annie Sullivan <sullivan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607874}

tools/perf/page_sets/rendering/tough_compositor_cases.py

@@ -50,20 +50,6 @@ class JSScrollTextPage(ToughCompositorScrollPage):
   URL = 'http://jsbin.com/dozirar/quiet?JS_SCROLL_TEXT_ONLY'
 
 
-# Why: Scroll by a large number of CC layers """
-# TODO(crbug.com/878951): Remove after 'n_layer' tests below are fully landed.
-class CCScroll200LayerPage(ToughCompositorScrollPage):
-  BASE_NAME = 'cc_scroll_200_layer_grid'
-  URL = 'http://jsbin.com/yakagevo/1/quiet?CC_SCROLL_200_LAYER_GRID'
-
-
-# Why: Scroll by a large number of JS layers """
-# TODO(crbug.com/878951): Remove after 'n_layer' tests below are fully landed.
-class JSScroll200LayerPage(ToughCompositorScrollPage):
-  BASE_NAME = 'js_scroll_200_layer_grid'
-  URL = 'http://jsbin.com/jumolix/quiet?JS_SCROLL_200_LAYER_GRID'
-
-
 class ToughCompositorWaitPage(ToughCompositorPage):
   ABSTRACT_STORY = True