win: Try to make midl.py work with midl.exe 8.1.620

Bug: 756607
Change-Id: I78e1fdf2411c067efd5423987ab9812f14b93736
Reviewed-on: https://chromium-review.googlesource.com/680041Reviewed-by: Scott Graham <scottmg@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#504255}

build/config/win/BUILD.gn

@@ -427,13 +427,3 @@ config("target_winrt") {
     "/EHsc",
   ]
 }
-
-# Internal stuff --------------------------------------------------------------
-
-# Config used by the MIDL template to disable warnings.
-config("midl_warnings") {
-  if (is_clang) {
-    # MIDL generates code like "#endif !_MIDL_USE_GUIDDEF_".
-    cflags = [ "-Wno-extra-tokens" ]
-  }
-}

build/toolchain/win/midl.gni

@@ -92,7 +92,5 @@ template("midl") {
     public_deps = [
       ":$action_name",
     ]
-
-    configs += [ "//build/config/win:midl_warnings" ]
   }
 }

build/toolchain/win/midl.py

@@ -36,6 +36,16 @@ def ZapTimestamp(filename):
         'target_arch=(AMD64|X86) 8\.\d\d\.\d{4}',
         '    Oicf, W1, Zp8, env=\\1 (32b run), target_arch=\\2 8.xx.xxxx',
         contents)
+    # TODO(thakis): If we need more hacks than these, try to verify checked-in
+    # outputs when we're using the hermetic toolchain.
+    # midl.exe older than 8.1.622 omit '//' after #endif, fix that:
+    contents = contents.replace('#endif !_MIDL_USE_GUIDDEF_',
+                                '#endif // !_MIDL_USE_GUIDDEF_')
+    # midl.exe puts the midl version into code in one place.  To have
+    # predictable output, lie about the midl version if it's not 8.1.622.
+    # This is unfortunate, but remember that there's beauty too in imperfection.
+    contents = contents.replace('0x801026c, /* MIDL Version 8.1.620 */',
+                                '0x801026e, /* MIDL Version 8.1.622 */')
   open(filename, 'wb').write(contents)