vendor: update clang/lld version to fix #13972

This seems like some sort of a weird linker bug, so just update the
toolchain a bit.

script/update-clang.sh

@@ -8,10 +8,10 @@
 # Do NOT CHANGE this if you don't know what you're doing -- see
 # https://code.google.com/p/chromium/wiki/UpdatingClang
 # Reverting problematic clang rolls is safe, though.
-CLANG_REVISION=307486
+CLANG_REVISION=308728
 
 # This is incremented when pushing a new build of Clang at the same revision.
-CLANG_SUB_REVISION=1
+CLANG_SUB_REVISION=3
 
 PACKAGE_VERSION="${CLANG_REVISION}-${CLANG_SUB_REVISION}"
 

vendor/libchromiumcontent

@@ -1 +1 @@
-Subproject commit 028b0af83076cec898f4ebce208b7fadb715656e
+Subproject commit 657a0c84482e296e2a4df63b49e4638faa8fee72