Really disable clang's SLP vectorizer on Linux.

Follow-up to https://codereview.chromium.org/393193003/ .
-fno-slp-vectorize was passed before -O2 on linux, and -O2 would
reenable it. I checked that the order of -O3 and -fno-slp-vectorize
is correct as-is on Mac.

BUG=none
NOTRY=true

Review URL: https://codereview.chromium.org/408523002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284191 0039d316-1c4b-4281-b951-d872f2087c98

build/common.gypi

@@ -3542,6 +3542,9 @@
                 'cflags!': [
                   '-fno-ident',
                 ],
+                # TODO(thakis): Remove once http://llvm.org/PR20354 is fixed
+                # and the fix is in chromium.
+                'cflags': [ '-fno-slp-vectorize', ],
               }],
               ['profiling==1', {
                 'cflags': [
@@ -3902,10 +3905,6 @@
               # code generated by flex (used in angle) contains that keyword.
               # http://crbug.com/255186
               '-Wno-deprecated-register',
-
-              # TODO(thakis): Remove once http://llvm.org/PR20354 is fixed
-              # and the fix is in chromium.
-              '-fno-slp-vectorize',
             ],
             'cflags!': [
               # Clang doesn't seem to know know this flag.