Tweak libpng encoding parameters to increase speed on very large images.

ui/gfx/BUILD.gn

Index: ui/gfx/BUILD.gn
diff --git a/ui/gfx/BUILD.gn b/ui/gfx/BUILD.gn
index ffabe80ad05b75caa664d16a6247a8aff9b78e68..883feca2db4e374c33d1bd6c0bc19080631eb5dd 100644
--- a/ui/gfx/BUILD.gn
+++ b/ui/gfx/BUILD.gn
@@ -689,6 +689,23 @@ source_set("test_support") {
   }
 }
 
+test("gfx_perftests") {
+  sources = [
+    "codec/png_codec_perftest.cc",
+  ]
+  data = [
+    "test/data/",
+  ]
+  deps = [
+    ":gfx",
+    "//base",
+    "//cc",

[danakj, 2016/04/22 20:29:45]

Hmmm, I wish that LapTimer was in cc:test_support, but we use it for telemetry
tests which have support built into the binary.

LGTM I suppose for the dep.

+    "//testing/gtest",
+    "//testing/gtest:gtest_main",
+    "//testing/perf",
+  ]
+}
+
 test("gfx_unittests") {
   sources = [
     "font_render_params_linux_unittest.cc",