Roll clang 274369:277642.

build/toolchain/toolchain.gni

Index: build/toolchain/toolchain.gni
diff --git a/build/toolchain/toolchain.gni b/build/toolchain/toolchain.gni
index 0dde8d9f1d1e4b20657f8fedc6224dfee1a64343..56e7ccb4555775428cbdfea363fc4c5988c70f38 100644
--- a/build/toolchain/toolchain.gni
+++ b/build/toolchain/toolchain.gni
@@ -22,31 +22,15 @@ declare_args() {
   # build/config/compiler/BUILD.gn).
   use_lld = is_win && host_os != "win"
 
-  # If this is set to true, or if LLVM_FORCE_HEAD_REVISION is set to 1
-  # in the environment, we use the revision in the llvm repo to determine
-  # the CLANG_REVISION to use, instead of the version hard-coded into
-  # //tools/clang/scripts/update.py. This should only be used in
-  # conjunction with setting LLVM_FORCE_HEAD_REVISION in the
-  # environment when `gclient runhooks` is run as well.
-  llvm_force_head_revision = false
-
   # Compile with Xcode version of clang instead of hermetic version shipped
   # with the build. Used on iOS to ship official builds (as they are built
   # with the version of clang shipped with Xcode).
   use_xcode_clang = is_ios && is_official_build
 }
 
-declare_args() {
-  if (is_clang) {
-    # Clang compiler version. Clang files are placed at version-dependent paths.
-    clang_version = "3.9.0"
-
-    if (llvm_force_head_revision) {
-      # TODO(hans): Remove after next Clang roll.
-      # ToT Clang has a higher version number.
-      clang_version = "4.0.0"
-    }
-  }
+if (is_clang) {
+  # Clang compiler version. Clang files are placed at version-dependent paths.
+  clang_version = "4.0.0"
 }
 
 # Check target_os here instead of is_ios as this file is loaded for secondary