Enable precompiled headers for Blink on Windows.

third_party/WebKit/Source/modules/webgl/BUILD.gn

 # Copyright 2016 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("//third_party/WebKit/Source/modules/modules.gni")
 
 blink_modules_sources("webgl") {
   sources = [
     "ANGLEInstancedArrays.cpp",
     "ANGLEInstancedArrays.h",
@@ skipping 105 matching lines @@
     "WebGLTransformFeedback.h",
     "WebGLUniformLocation.cpp",
     "WebGLUniformLocation.h",
     "WebGLVertexArrayObject.cpp",
     "WebGLVertexArrayObject.h",
     "WebGLVertexArrayObjectBase.cpp",
     "WebGLVertexArrayObjectBase.h",
     "WebGLVertexArrayObjectOES.cpp",
     "WebGLVertexArrayObjectOES.h",
   ]
+
+  # The modules/webgl/ directly is a larger module, and
+  # the implementation depends on a fair chunk of core/ --
+  # include the core pch for faster Windows compilation times.
+  configs += [ "//third_party/WebKit/Source/core:blink_core_pch" ]
 }