Roll clang 274369:277962.

build/toolchain/toolchain.gni

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Toolchain-related configuration that may be needed outside the context of the
 # toolchain() rules themselves.
 
 import("//build/config/chrome_build.gni")
 
 declare_args() {
@@ skipping 21 matching lines @@
 
   # 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"
-    }
+    clang_version = "4.0.0"
   }
 }
 
 # Check target_os here instead of is_ios as this file is loaded for secondary
 # toolchain (host toolchain in particular) but the argument is the same for
 # all toolchains.
 assert(!use_xcode_clang || target_os == "ios",
        "Using Xcode's clang is only supported in iOS builds")
 
 # Subdirectory within root_out_dir for shared library files.
@@ skipping 39 matching lines @@
 stamp_description = "STAMP {{output}}"
 copy_description = "COPY {{source}} {{output}}"
 if (host_os == "win") {
   stamp_command = "$python_path gyp-win-tool stamp {{output}}"
   copy_command =
       "$python_path gyp-win-tool recursive-mirror {{source}} {{output}}"
 } else {
   stamp_command = "touch {{output}}"
   copy_command = "ln -f {{source}} {{output}} 2>/dev/null || (rm -rf {{output}} && cp -af {{source}} {{output}})"
 }