Roll clang 241602:242792

A fairly small roll, not much in it.
* Bump version from 3.7.0 to 3.8.0
* sdefresne's change to the plugin to emit warnings in files that have
  Developer in the path (system headers should still not warn by virtue of
  being system headers; clang doesn't emit warnings in system headers)

BUG=510886

Review URL: https://codereview.chromium.org/1238353002

Cr-Commit-Position: refs/heads/master@{#339838}

tools/clang/scripts/update.py

@@ -410,6 +410,7 @@ def UpdateClang(args):
       try:
         DownloadUrl(cds_full_url, f)
         f.seek(0)
+        # TODO(thakis): Delete LLVM_BUILD_DIR before extracting.
         tarfile.open(mode='r:gz', fileobj=f).extractall(path=LLVM_BUILD_DIR)
         print 'clang %s unpacked' % PACKAGE_VERSION
         # Download the gold plugin if requested to by an environment variable.

tools/clang/scripts/update.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=241602
+CLANG_REVISION=242792
 
 # This is incremented when pushing a new build of Clang at the same revision.
-CLANG_SUB_REVISION=3
+CLANG_SUB_REVISION=1
 
 PACKAGE_VERSION="${CLANG_REVISION}-${CLANG_SUB_REVISION}"