[AUTO_UPDATE] Copying from upstream Mojo Repository

config/compiler/BUILD.gn

diff --git a/config/compiler/BUILD.gn b/config/compiler/BUILD.gn
index 5bbf619..d570de1 100644
--- a/config/compiler/BUILD.gn
+++ b/config/compiler/BUILD.gn
@@ -16,6 +16,8 @@
 import("//build/config/nacl/config.gni")
 import("//build/toolchain/ccache.gni")
 import("//build/config/sanitizers/sanitizers.gni")
+# XXX(smklein): Added so I could include mojo_mst_root below
+import("//build/module_args/mojo.gni")
 
 declare_args() {
   # Normally, Android builds are lightly optimized, even for debug builds, to
@@ -59,6 +61,10 @@
 config("default_include_dirs") {
   include_dirs = [
     "//",
+    # XXX(smklein): Added this mojo_mst_root so #includes will work when relying
+    # on files in the MST. I am not sure this is an appropriate location for
+    # this include_dir, however.
+    mojo_mst_root,
     root_gen_dir,
   ]
 }

module_args/mojo.gni

diff --git a/module_args/mojo.gni b/module_args/mojo.gni
index e3c88d2..e55b53d 100644
--- a/module_args/mojo.gni
+++ b/module_args/mojo.gni
@@ -5,6 +5,10 @@
 # This variable should point to the parent directory of the Mojo SDK.
 mojo_sdk_root = "//"
 
+# This variable should point to the parent directory of the Mojo MST.
+# XXX(smklein): Is this the right location for this root? Questionable.
+mojo_mst_root = "//mst"
+
 # To build the Mojo shell from source, set this variable to true. To use the
 # prebuilt shell, omit this variable or set it to false. Note that the prebuilt
 # shell will be used only on platforms for which it is published (currently