Disable clang's SLP vectorizer.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index fb53e9264fb6062ca559700f1a3ab9a21ea5aca0..451e4bdf480aec33415938fba9bbefd714254f76 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -3903,6 +3903,10 @@
               # 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.
@@ -4743,6 +4747,11 @@
                 # cfe-dev discussion.
                 '-Wno-selector-type-mismatch',
               ],
+              'OTHER_CFLAGS': [
+                # TODO(thakis): Remove once http://llvm.org/PR20354 is fixed
+                # and the fix is in chromium.
+                '-fno-slp-vectorize',
+              ],
 
               'conditions': [
                 ['clang_xcode==0', {