Remove SK_DISABLE_PIXELREF_LOCKCOUNT_BALANCE_CHECK.

skia/BUILD.gn

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 if (cpu_arch == "arm") {
   import("//build/config/arm.gni")
 }
 
@@ skipping 146 matching lines @@
     # skia uses static initializers to initialize the serialization logic
     # of its "pictures" library. This is currently not used in chrome; if
     # it ever gets used the processes that use it need to call
     # SkGraphics::Init().
     "SK_ALLOW_STATIC_GLOBAL_INITIALIZERS=0",
 
     # Forcing the unoptimized path for the offset image filter in skia until
     # all filters used in Blink support the optimized path properly
     "SK_DISABLE_OFFSETIMAGEFILTER_OPTIMIZATION",
 
-    # Disable this check because it is too strict for some Chromium-specific
-    # subclasses of SkPixelRef. See bug: crbug.com/171776.
-    "SK_DISABLE_PIXELREF_LOCKCOUNT_BALANCE_CHECK",
-
     "IGNORE_ROT_AA_RECT_OPT",
 
     "SK_IGNORE_BLURRED_RRECT_OPT",
 
     "SK_IGNORE_QUAD_RR_CORNERS_OPT",
 
     # this flag forces Skia not to use typographic metrics with GDI.
     "SK_GDI_ALWAYS_USE_TEXTMETRICS_FOR_FONT_METRICS",
 
     "SK_USE_DISCARDABLE_SCALEDIMAGECACHE",
@@ skipping 478 matching lines @@
     ":skia_config",
     "//build/config/compiler:no_chromium_code"
   ]
 
   deps = [
     "//base",
   ]
 
   visibility = ":skia"
 }