Turn on clang by default on linux, 2nd try.

This is mostly to collect performance and size data for now. Unless things
look really good, I'm going to revert this by wednesday morning (PDT).

BUG=360311
TBR=awong@chromium.org

Review URL: https://codereview.chromium.org/380573002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@281914 0039d316-1c4b-4281-b951-d872f2087c98

build/common.gypi

@@ -1777,6 +1777,10 @@
         # the class names, so the JNI generator needs to know this.
         'jni_generator_jarjar_file': '../android_webview/build/jarjar-rules.txt',
       }],
+      ['OS=="linux"', {
+        # TODO(thakis): This is here to measure perf for a while.
+        'clang%': 1,
+      }],  # OS=="mac"
       ['OS=="mac"', {
         'conditions': [
           # All Chrome builds have breakpad symbols, but only process the

tools/clang/scripts/update.sh

@@ -137,12 +137,6 @@ while [[ $# > 0 ]]; do
   shift
 done
 
-# Remove clang on bots where it was autoinstalled in r262025.
-if [[ -f "${LLVM_BUILD_DIR}/autoinstall_stamp" ]]; then
-  echo Removing autoinstalled clang and clobbering
-  rm -rf "${LLVM_BUILD_DIR}"
-fi
-
 if [[ -n "$if_needed" ]]; then
   if [[ "${OS}" == "Darwin" ]]; then
     # clang is used on Mac.
@@ -154,6 +148,12 @@ if [[ -n "$if_needed" ]]; then
     # clang previously downloaded, remove third_party/llvm-build to prevent
     # updating.
     true
+  elif [[ "${OS}" == "Linux" ]]; then
+    # Temporarily use clang on linux. Leave a stamp file behind, so that
+    # this script can remove clang again on machines where it was autoinstalled.
+    mkdir -p "${LLVM_BUILD_DIR}"
+    touch "${LLVM_BUILD_DIR}/autoinstall_stamp"
+    true
   else
     # clang wasn't needed, not doing anything.
     exit 0