Fix LayerTreeHostFiltersPixelTest.BackgroundFilterBlurOutsets has 3474 pixel...

Fix LayerTreeHostFiltersPixelTest.BackgroundFilterBlurOutsets has 3474 pixel differences on Loongson.

Set percentage_pixels_large_error on Loongson.

BUG= 819110
R= fsamuel@chromium.org

Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I680f9c5f2eb36f8387bf4e5edf5cfe19da2108e3
Reviewed-on: https://chromium-review.googlesource.com/1023710Reviewed-by: enne <enne@chromium.org>
Commit-Queue: 汪 清 <wangqing-hf@loongson.cn>
Cr-Commit-Position: refs/heads/master@{#552961}

cc/trees/layer_tree_host_pixeltest_filters.cc

@@ -79,9 +79,14 @@ TEST_F(LayerTreeHostFiltersPixelTest, BackgroundFilterBlurOutsets) {
       5.f, SkBlurImageFilter::kClamp_TileMode));
   blur->SetBackgroundFilters(filters);
 
+#if defined(OS_WIN) || defined(_MIPS_ARCH_LOONGSON)
 #if defined(OS_WIN)
   // Windows has 5.9325% pixels by at most 2: crbug.com/259922
   float percentage_pixels_large_error = 6.0f;
+#else
+  // Loongson has 8.685% pixels by at most 2: crbug.com/819110
+  float percentage_pixels_large_error = 8.7f;
+#endif
   float percentage_pixels_small_error = 0.0f;
   float average_error_allowed_in_bad_pixels = 2.f;
   int large_error_allowed = 2;