Share precompiled header setup for blink between Windows and Mac.

third_party/WebKit/Source/core/BUILD.gn

Index: third_party/WebKit/Source/core/BUILD.gn
diff --git a/third_party/WebKit/Source/core/BUILD.gn b/third_party/WebKit/Source/core/BUILD.gn
index 4345d43272e133cfb4e0464f97ad3177d9427e16..41291a351d9154e815b5c671979c3d1956e6c18f 100644
--- a/third_party/WebKit/Source/core/BUILD.gn
+++ b/third_party/WebKit/Source/core/BUILD.gn
@@ -66,6 +66,10 @@ config("blink_core_pch") {
 
       # Force include the header.
       cflags = [ "/FI$precompiled_header" ]
+    } else if (is_mac) {
+      precompiled_header = rebase_path("mac/Precompile-core.h", root_build_dir)
+      precompiled_source =
+          "//third_party/WebKit/Source/core/mac/Precompile-core.h"
     }
   }
 }
@@ -132,10 +136,6 @@ source_set("prerequisites") {
     "//third_party/WebKit/Source:inside_blink",
   ]
 
-  if (is_mac) {
-    public_configs += [ "//third_party/WebKit/Source:mac_precompiled_headers" ]
-  }
-
   if (use_openmax_dl_fft) {
     deps += [ "//third_party/openmax_dl/dl" ]
   }