www-client/chromium: fix build with clang

Closes: https://bugs.gentoo.org/637654
Package-Manager: Portage-2.3.19_p1, Repoman-2.3.6_p35

www-client/chromium/chromium-64.0.3282.24.ebuild

@@ -147,6 +147,7 @@ PATCHES=(
 	"${FILESDIR}/chromium-webrtc-r0.patch"
 	"${FILESDIR}/chromium-memcpy-r0.patch"
 	"${FILESDIR}/chromium-cups-r0.patch"
+	"${FILESDIR}/chromium-clang-r2.patch"
 )
 
 pre_build_checks() {

www-client/chromium/files/chromium-clang-r2.patch

@@ -0,0 +1,21 @@
+--- a/build/config/compiler/BUILD.gn
++++ b/build/config/compiler/BUILD.gn
+@@ -422,18 +422,6 @@
+     cflags += [ "-fcolor-diagnostics" ]
+   }
+ 
+-  # TODO(hans): Remove this once Clang generates better optimized debug info by
+-  # default. https://crbug.com/765793
+-  if (is_clang && !is_nacl && current_toolchain == host_toolchain &&
+-      target_os != "chromeos") {
+-    cflags += [
+-      "-Xclang",
+-      "-mllvm",
+-      "-Xclang",
+-      "-instcombine-lower-dbg-declare=0",
+-    ]
+-  }
+-
+   # Print absolute paths in diagnostics. There is no precedent for doing this
+   # on Linux/Mac (GCC doesn't support it), but MSVC does this with /FC and
+   # Windows developers rely on it (crbug.com/636109) so only do this on Windows.