Merge Compositor's ScrollbarAnimationControllers into single class

This patch is for merge ScrollbarAnimationControllerLinearFade and
ScrollbarAnimationControllerThinning into ScrollbarAnimationController.

BUG=656606
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

Review-Url: https://codereview.chromium.org/2692243005
Cr-Commit-Position: refs/heads/master@{#451397}

diff --git a/cc/BUILD.gn b/cc/BUILD.gn
index 1d17fc8..c0bbd2b0 100644
--- a/cc/BUILD.gn
+++ b/cc/BUILD.gn

@@ -70,10 +70,6 @@
     "input/scroll_state_data.h",
     "input/scrollbar_animation_controller.cc",
     "input/scrollbar_animation_controller.h",
-    "input/scrollbar_animation_controller_linear_fade.cc",
-    "input/scrollbar_animation_controller_linear_fade.h",
-    "input/scrollbar_animation_controller_thinning.cc",
-    "input/scrollbar_animation_controller_thinning.h",
     "input/selection.h",
     "input/single_scrollbar_animation_controller_thinning.cc",
     "input/single_scrollbar_animation_controller_thinning.h",
@@ -755,8 +751,7 @@
     "debug/rendering_stats_unittest.cc",
     "input/browser_controls_offset_manager_unittest.cc",
     "input/scroll_state_unittest.cc",
-    "input/scrollbar_animation_controller_linear_fade_unittest.cc",
-    "input/scrollbar_animation_controller_thinning_unittest.cc",
+    "input/scrollbar_animation_controller_unittest.cc",
     "input/single_scrollbar_animation_controller_thinning_unittest.cc",
     "ipc/cc_param_traits_unittest.cc",
     "ipc/struct_traits_unittest.cc",