Android WebView: build fixes for use_system_skia.

build/shim_headers.gypi

Index: build/shim_headers.gypi
diff --git a/build/shim_headers.gypi b/build/shim_headers.gypi
index 4291468de106a6a38a033c391199e7b3eb3da52f..997a4d0b0f558f65f5a107977c3630001f69126a 100644
--- a/build/shim_headers.gypi
+++ b/build/shim_headers.gypi
@@ -17,12 +17,19 @@
     '<(shim_headers_path)',
   ],
   'all_dependent_settings': {
+    # Repeating this with different numbers of plusses is unfortunately required
+    # to make sure that even if this include is inside nested conditions/etc, it
+    # still gets inserted at the beginning of the include_dirs list. See
+    # http://crbug.com/263818 for details.
     'include_dirs+++': [
       '<(shim_headers_path)',
     ],
     'include_dirs++++': [
       '<(shim_headers_path)',
     ],
+    'include_dirs+++++': [
+      '<(shim_headers_path)',
+    ],
   },
   'actions': [
     {