Move scaling of ui resources for scrollbars to the time of upload

cc/trees/layer_tree_host_pixeltest_scrollbars.cc

Index: cc/trees/layer_tree_host_pixeltest_scrollbars.cc
diff --git a/cc/trees/layer_tree_host_pixeltest_scrollbars.cc b/cc/trees/layer_tree_host_pixeltest_scrollbars.cc
index 0c9f24cfcc08eabd4061e15f6d41fd0194b87382..02bbd929ad3beee7929098c70a567adfe304066e 100644
--- a/cc/trees/layer_tree_host_pixeltest_scrollbars.cc
+++ b/cc/trees/layer_tree_host_pixeltest_scrollbars.cc
@@ -10,6 +10,7 @@
 #include "cc/layers/painted_scrollbar_layer.h"
 #include "cc/layers/solid_color_layer.h"
 #include "cc/test/layer_tree_pixel_test.h"
+#include "cc/test/pixel_comparator.h"
 #include "cc/test/test_in_process_context_provider.h"
 #include "gpu/command_buffer/client/gles2_interface.h"
 
@@ -163,6 +164,18 @@ TEST_F(LayerTreeHostScrollbarsPixelTest, HugeTransformScale) {
   scale_transform.Scale(scale, scale);
   layer->SetTransform(scale_transform);
 
+  // The inner edge is antialiased and gets off-by-one differences.
+  float percentage_pixels_large_error = 0.42f;
+  float percentage_pixels_small_error = 0.f;
+  float average_error_allowed_in_bad_pixels = 1.f;
+  int large_error_allowed = 1;
+  int small_error_allowed = 0;
+  pixel_comparator_.reset(new FuzzyPixelComparator(
+      true,  // discard_alpha
+      percentage_pixels_large_error, percentage_pixels_small_error,
+      average_error_allowed_in_bad_pixels, large_error_allowed,
+      small_error_allowed));
+
   RunPixelTest(PIXEL_TEST_GL, background,
                base::FilePath(FILE_PATH_LITERAL("spiral_64_scale.png")));
 }